decapod crustaceans from the maastrichtian fox hills formation

Decapod Crustaceans from the Maastrichtian Fox Hills Formation

Robert S. Crawford, Rodney M. Feldmann,David A. Waugh, Brian M. Kelley and Joel G. Allen

Department of Geology, Kent State University, Kent, OH 44242 USAemail: [email protected]

AbstractExamination of all known specimens of decapod crustaceans from the Fox Hills Formation hasresulted in recognition of five species and three distinctly different forms of pereiopods that can-not be assigned to a recognized taxon with certainty. Callichirus waagei n. sp. is proposed for acallianassid claw preserved within an Ophiomorpha burrow. Hoploparia sp. and Raninella oa-heensis Bishop, 1978, are reported from the formation for the first time, and the cheliped of thelatter species is noted, also for the first time. Latheticocarcinus shapiroi Bishop, 1988, the mostcommon species of decapod in the formation, is re-described; the lateral flanks of this homolidcrab are recognized for the first time, and the carapace is reconstructed. Necrocarcinus siouxensisFeldmann, Awotua and Welshenbaugh, 1976, is noted, but no new specimens were studied. All thedecapods were preserved within concretions and all but one specimen of Hoploparia were disar-ticulated elements, suggesting that they may have been molted remains. Cuticle was well pre-served and thin section examination of the lamellar structure of Hoploparia cuticle confirmedthat, although thoroughly altered chemically, details of lamellar structure are retained.

KeywordsSystematic paleontology, new species, taphonomy, cuticle microstructure, Callichirus, Hoploparia,Latheticocarcinus, Raninella, pereiopods.

Introduction

The Fox Hills Formation, exposed in parts ofSouth Dakota, North Dakota, Wyoming, Mon-tana, and Colorado, is part of the final marine de-positional sequence of the Cretaceous WesternInterior Seaway. It has been of interest since themiddle of the 19th century, when Meek and Hay-den (1856a, 1856b, 1856c, 1856d, 1856e) con-ducted the first study of its fauna and stratigraphicrelationships. The compilation of that work(Meek 1876) served as a comprehensive guide tothe fauna of the Fox Hills Formation as late as the1960s. A detailed history of the investigations ofthe type area of the Fox Hills Formation can befound in Feldmann (1967) and Waage (1968). Arenewed interest in the Late Cretaceous extinc-

tion, coupled with a more complete understand-ing of paleobiology and paleoecology, stimulatednew investigations into the Fox Hills Formationduring the 1960s and early 1970s (see Waage 1961,1964, 1968; Feldmann 1967, 1972; Speden 1970;Erickson 1973, 1974, 1978; Feldmann and Palub-niak 1975). Subsequently, Carpenter et al. (1988),Erickson (1992), Erickson and Hoganson (1992),Landman and Cobban (2003), and Cochran et al.(2003) have continued investigations into the FoxHills Formation and the Late Cretaceous Maas-trichtian Seaway.

Here we document all known occurrences ofdecapods from the Fox Hills Formation of SouthDakota, North Dakota, and Wyoming; describetheir stratigraphic and geographic occurrences(Appendices A, B and C); and summarize the

Bulletin of the Peabody Museum of Natural History 47(1–2):3–28, October 2006.© 2006 Peabody Museum of Natural History, Yale University. All rights reserved. — www.peabody.yale.edu

taphonomic processes that led to their preserva-tion. Recent examination of concretions previouslycollected by K. M. Waage and others has yieldednew decapod specimens, including previously un-known portions of the homolid Latheticocarcinusshapiroi Bishop, 1983, a new species of callianasidshrimp, Callichirus waagei (see descriptionbelow), several new occurrences of other decapods,and an assortment of various decapod appendages.

Repositories for cited specimens are thePeabody Museum of Natural History,Yale Univer-sity, New Haven, Connecticut, USA (YPM) andthe North Dakota State Fossil Collection, NorthDakota Geological Survey, Bismarck, NorthDakota, USA (ND).

General Setting

The Fox Hills Formation records the latest marineregressive depositional sequence of the Late Creta-ceous Maastrichtian Seaway, which includes shal-low marine shelf through delta-plain facies

(Erickson 1992). The formation has been subdi-vided into three members: the shale dominatedTrail City Member, the sandstone dominatedTimber Lake Member, and the intercalated shaleand sandstone of the Iron Lightning Member. Avariety of marine and nonmarine depositionalsettings has been inferred, including a delta plat-form, barrier islands, tidal inlets, distributaries, in-terdistributary bays, and the Dakota Isthmus(Erickson 1992).

The fossils of the Fox Hills Formation arecharacterized by their abundance, diversity, andexcellent preservation (Speden 1970). They aretypically found within concretions, and are gener-ally scarce within the enclosing sediment. Rangingin size from 17 cm to 1.8 m in diameter, the con-cretions occur in vertically constrained horizonsand are stacked in successive layers (Speden 1970).The distribution of fossils within the concretion-ary layers is highly variable, with some concretionsbeing barren, and others containing hundreds, oreven thousands, of fossils (Waage 1968:73).

Figure 1. The sites in South Dakota and North Dakota from which the decapod crustaceans described in thisstudy were collected. Sites for previously described decapods from the Fox Hills Formation are not shown, noris that of the single specimen of Hoploparia sp. collected from Niobrara County, Wyoming. Precise locationsare given in Appendices A, B and C. A, A0285, A0296; B, A0272; C, A0313; D, A0549, A4659; E, A0642, A0643,A0644, A0958; F, A4665, A0270; G, A0209; H, A0713; I, A1138; J, A0673; K, collection locality for Callichiruswaagei; L, collection locality for Hoploparia sp. at Beaver Bay, Emmons County, North Dakota.

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A generally uniform array of taxa has beenrecognized within the Fox Hills Formation, withmany of the taxa ranging throughout the TrailCity and Timber Lake members. The faunal as-semblages are comprised primarily of pelecypods,with ammonites and gastropods in lesser quanti-ties (Waage 1968). It is typical for one bivalvespecies to comprise as much as 95% of the fauna.Decapods are far less abundant. The fossil brach-yuran decapods (crabs) are generally inconspicu-ous elements in mollusc-rich concretions,whereas the lobster remains occur in otherwisebarren concretions in the Timber Lake Member.Fossil crabs are largely confined to exposuresalong the Grand River in South Dakota (Figure 1),whereas isolated lobster remains are noted inNorth Dakota, South Dakota, and Wyoming. Thesole specimen of callianassid is preserved withinan Ophiomorpha burrow collected in SouthDakota from the Timber Lake Member.

In addition to being rare, the crabs in the FoxHills Formation are extremely small. The scarcityand the small size of the crabs, coupled with therarity of the lobsters and callianassids, largely ex-plains why it has taken so long to amass enoughmaterial for study.

Other Decapod Occurrences

Before this work there have been only three oc-currences of decapods from the Fox Hills Forma-tion. Waage (1968) illustrated a callianassid clawpreserved within a burrow referable to Ophio-morpha Lundgren, 1891, from the Timber LakeMember. Ophiomorpha-like burrows had previ-ously been attributed to the work of Callianassaor other callianassids in modern environments(Weimer and Hoyt 1964). However, until this ob-servation from Fox Hills ophiomorphid burrows,no fossil remains of the trace-maker had been re-ported. Thus, this discovery takes on additionalsignificance.

Subsequently, Feldmann et al. (1976) de-scribed Necrocarcinus siouxensis from the Tim-ber Lake Member in Sioux County, North Dakota.Their placement of the sole specimen discoveredin the genus Necrocarcinus Bell, 1863, rather thanCenomanocarcinus Van Straelen, 1936, supportedthe position held by Wright and Collins (1972)that Cenomanocarcinus and Orithopsis Carter,1872, were junior subjective synonyms of Necro-

carcinus. Before that, Förster (1968) consideredthe genera to be distinct from one another. In a re-cent review of calappoid crabs, Schweitzer andFeldmann (2000a) discussed these and other fos-sils, elevated the Necrocarcininae Förster, 1968, tofamily level, and recognized the genera discussedabove as distinct, a position further discussed bySchweitzer et al. (2003). Therefore, the Fox Hillsspecimen is referable to Cenomanocarcinus, anaffinity originally discussed by Feldmann et al.(1976).

Finally, Bishop (1988) described Lathetico-carcinus shapiroi from the Fox Hills Formation inCorson County, South Dakota, and possibly alsofrom near Redbird, Niobrara County, Wyoming.He assigned the specimens to the DakoticancridaeRathbun, 1917, and suggested that the genuscould have descended from either DakoticancerRathbun, 1917, or Tetracarcinus Weller, 1905.This species, here placed within the Homolidae, isdiscussed in detail below.

Systematic Paleontology

Order Decapoda Latreille, 1802Family Nephropidae Dana, 1852Genus Hoploparia McCoy, 1849

Type species. Astacus longimanus Sowerby, 1826, by subse-quent designation of Rathbun, 1926.

Hoploparia sp.Figure 2.

Material examined. YPM 203892, 203897, 203898 and ND05-1.1.

Localities and stratigraphic position. See Appendix A for spe-cific locality information. YPM 203892 was collected from theTrail City Member of the Fox Hills Formation at locality A0673of Waage, Dewey County, South Dakota. YPM 203897 and203898 were collected from a massive marine sand lithofaciesof the Fox Hills Formation at Localities D6293 and A4754, re-spectively, of Waage, Niobrara County, Wyoming. ND05-1.1was collected from the Timber Lake Member of the Fox HillsFormation at Beaver Bay, about 21 km west from Linton, Em-mons County, North Dakota. All are Maastrichtian in age.

Description of material. The carapace and abdomen are pre-sent on ND05-1.1; however, both are incomplete and poorlypreserved. The cuticle has been altered to a dense, dark mater-ial that readily breaks with a conchoidal fracture. Therefore, thenature of surface features is difficult to discern. Only the pos-teroventral portion of the carapace is preserved and it appearsto be smooth. The abdomen is represented by fragments ofsomites 2 through 6 and the exopod of the uropod. The sur-

Decapod crustaceans from the Maastrichtian Fox Hills Formation • Crawford et al. 5

faces of the terga seem generally smooth and lack keels. Theterga of somites 4 and 5 are separated from the pleura by a con-cave-upward ridge joining the points of articulation. Thepleura are triangular, apparently smooth, and terminate inposteriorly directed sharp tips. The exopod of the uropod isnearly circular and bears a diaresis.

Crusher claws are present on all four specimens. Theclaws bear hands that are longer than high, with length toheight ratios ranging from 1.2 to 1.4. The greatest height isreached at the point of articulation of the dactylus. Theouter surface of the hands is smoothly convex and orna-mented by fine and very fine granules. The upper surfacebears at least four small spines and the lower surface appearsto be smooth. The inner surface is not exposed on any of thespecimens. The fixed finger on YPM 203897 is long (morethan 26 mm), whereas the hand of that specimen is 38.0 mmlong. The finger tapers distally and is slightly curved upward.The occlusal surface bears coarse, domed denticles proxi-mally and finer, domed denticles distally. The dactylus ismore slender, uniformly tapering distally, and also bearsdomed denticles where visible. Other elements of the legsconsist of long, slender, apparently smooth fragments.

Discussion. Four specimens referable to Ho-ploparia from localities in South Dakota, North

Dakota, and Wyoming constitute the first recordsof lobsters from the Fox Hills Formation. Al-though the claw morphology exhibited by thefour specimens is similar enough to suggest thatthey should be placed within a single species, thereis inadequate information about the carapace andabdomen to either assign the material to any de-scribed species or to name a new species.

Nephropid lobsters in the upper Midwesthave been assigned to two genera, Hoploparia andPaleonephrops Mertin, 1941. The primary distinc-tions between the two genera lie in the morphol-ogy of the carapace and abdomen. Paleonephropstends to have a coarsely ornamented cephalotho-rax, bearing rows of nodes, and keeled abdominalterga (Feldmann and McPherson 1980), neither ofwhich is evident on the Fox Hills specimens. Ho-ploparia has a carapace that is generally smoother,at least in the posteroventral portion, and an ab-domen on which the terga are not keeled. Thiscombination of characters is present on the exam-

Figure 2. Hoploparia sp. 1. Outer surface of left cheliped, YPM 203897. 2. Outer surface of left cheliped, ND05-1.1. 3. Posteroventral portion of cephalothorax, abdomen and uropod, ND05-1.1. Scale bars equal 1 cm.

6 Bulletin of the Peabody Museum of Natural History 47(1–2) • October 2006

ined specimens and, therefore, the material is as-signed to Hoploparia with confidence.

Within Hoploparia, assignment to speciescannot be made with certainty. Several specieshave been named in Late Cretaceous and Pale-ocene rocks of the region, but none bear the com-bination of characters of the abdomen and clawsdescribed above.

Hoploparia bearpawensis Feldmann in Feld-mann et al., 1977, from the late CampanianBearpaw Shale in eastern Montana, bears trans-verse nodes separating the abdominal terga fromthe pleura. The claws on this species are notknown. Hoploparia mickelsoni Bishop, 1985,from the early Campanian Pierre Shale in westernSouth Dakota, bears ridges, separating the ab-dominal terga from the pleura, that are very simi-lar to those on the Fox Hills specimens; however,the claws are much more elongate and slenderthan those from the Fox Hills Formation. Clawmorphology is known to differ considerablywithin species of the genus (Tshudy and Parsons1998) and, as a result, may not be a reliable mor-phological aspect for making species-level distinc-tions. Nonetheless, in the absence of morecomplete carapaces and abdomina, assignment ofthis material to H. mickelsoni cannot be donewith confidence. Hoploparia buntingi (Feldmannand Holland, 1971), from the Paleocene Cannon-ball Formation in southcentral North Dakota,bears claws that are much like those of the FoxHills specimens, though the abdomen of H.buntingi lacks arcuate transverse ridges.

Infraorder Thalassinidea Latreille, 1831Superfamily Callianassoidea Dana, 1852

Family Callianassidae Dana, 1852Subfamily Callichirinae Manning and Felder, 1991

Genus Callichirus Stimpson, 1866

Type species. Callianassa major Say, 1818, by original desig-nation.

Callichirus waagei n. sp.Figure 3, 1 and 3.

Callianassa sp. Waage, 1968: pl. 8C.

Types. The holotype, and sole specimen, YPM 35098.Locality and stratigraphic position. YPM 35098 was collectedfrom the Timber Lake Member of the Fox Hills Formation atlocality A0370 of Waage, in the lower 6 ft (2 m) of unit 1, 0.5miles south of Hump Creek, 1.2 miles east of SD Rt. 65, and 2.4

miles northeast of Black Horse, Corson County, South Dakota.

Etymology. The trivial name recognizes the contributions ofKarl Waage to the study of the type area of the Fox Hills For-mation and to his mentorship of many paleontology students.

Diagnosis. Propodus with distinct sulcus extending from dis-tal notch upward and paralleling articulation with dactylusand fixed finger with a few domed denticles.

Description. Inner surface of part of right merus, carpus, andpropodus generally smooth, crushed. Merus poorly preserved,length more than 10 mm, height approximately 2 mm; straightand apparently parallel-sided proximally, curving abruptly atdistal end to articulate with carpus near upper end of proximalend of carpus. Carpus longer (12.4 mm) than high (7.1 mm);generally rectangular with nearly parallel upper and lowermargins; upper margin weakly convex; proximal margin gen-erally perpendicular to long axis of carpus with deep, hemi-spherical concavity, 2.1 mm in diameter, arising 1.2 mm fromupper corner of carpus and forming socket of articulation withmerus; proximal margin smoothly convex from re-entrant tolower corner; distal margin obscured but seems to be perpen-dicular to long axis of the segment. Propodus more or lessquadrate, greatest height (7.2 mm) at proximal end of hand,tapering to 6.7 mm at base of fixed finger; length of hand 11.2mm; length of fixed finger 6.3 mm. Proximal end of handstraight, perpendicular to long axis of hand; upper marginweakly convex; lower margin, including finger, weakly concave;distal margin straight along articulation for dactylus with deep,distinct notch developed above fixed finger; notch extends up-ward slightly and continues onto hand as a shallow sulcus par-alleling articulation for dactylus. Fixed finger taperinguniformly distally, slightly upturned at distal extremity; oc-clusal surface with few small, domed denticles.

Discussion. The single specimen of C. waagei wasfirst noted and illustrated by Waage (1968: pl. 8C).The cheliped is preserved within an Ophiomor-pha burrow (Figure 3, 1 and 2), which is 36 mm indiameter externally and 20 mm in diameter inter-nally. The walls of the burrow are constructed ofpellets that are approximately 6 mm in diameter.The decapod specimen was examined by HenryRoberts of the Division of Crustacea, U. S. Na-tional Museum of Natural History, Washington,D.C., who identified it as Callianassa sp., thegenus to which the type species of Callichirus,along with most other members of the family,were assigned at that time. Subsequently, Man-ning and Felder (1986) clarified the definition ofCallichirus and then (Manning and Felder 1991)revised the Callianassidae, naming one new fam-ily, six new subfamilies (including the one towhich this specimen has been assigned), and twonew genera. Perhaps as important, they noted sev-eral characters of the chelipeds that were diagnos-


tic at the generic level. The general proportionsand outline of the merus, carpus, and propodus ofthe Fox Hills specimen closely conform to those ofthe major claw of extant Callichirus major.Therefore, the assignment of this material to Cal-lichirus is as secure as possible given that only asingle, partial cheliped is available for study.

Interestingly, the relationship of the fossil bur-

rows assigned to Ophiomorpha and the burrowsof extant ghostshrimp was most clearly articulatedby Weimer and Hoyt (1964); the direct analogythey drew was between the burrows of the livingCallianassa major (now Callichirus major) andOphiomorpha from the Fox Hills Formation inColorado. The general size relationships of theburrows as well as the general diameter of the pel-

Figure 3. Ophiomorpha Lundgren and Callichirus waagei n. sp. 1. Axial section of Ophiomorpha burrow, YPM35099, showing the thickness of the pelleted wall and the position of the sole specimen of Callichirus waagei.2. Outer surface of the same specimen showing the distribution of pellets. 3. Merus, carpus and propodus ofholotype of Callichirus waagei n. sp., YPM 35098.


lets from which the walls are constructed arenearly identical in the fossil and modern burrows.Further, the burrows of both the living and thefossil organisms occur in coarse to medium sandof intertidal or shallow subtidal origin. Subse-quently, Bishop and Bishop (1992) cautioned thatsimilar burrow structures can be produced by dif-ferent ghost shrimp and the same taxon of ghostshrimp can produce different burrow structures.

Callichirus has been reported only once be-fore from the fossil record. Feldmann and Zins-meister (1984) identified Callianassa symmetricafrom specimens collected from Eocene erratics inthe McMurdo area of Antarctica. Subsequently,Stillwell et al. (1997) reassigned the specimens ten-tatively to Callichirus, based on the revision ofManning and Felder (1991), and noted their pres-ence in Ophiomorpha-like burrows that were lessknobby than typical forms. Schweitzer and Feld-mann (2000b) also questionably assigned theoriginal material and additional specimens toCallichirus, based on the morphology of a poorlypreserved merus, and also described the burrowmorphology and composition in greater detail.The Antarctic material, as with the Fox Hills spec-imen, was preserved in a sandstone interpreted tobe of shallow subtidal origin.

Order Brachyura Latreille, 1802Section Podotremata Guinot ,1977

Superfamily Homoloidea de Haan, 1839Family Homolidae de Haan, 1839

Type genus. Homola Leach, 1815.

Included fossil genera. Dagnaudus Guinot and Richer deForge, 1995; Gastrodorus von Meyer, 1864; Homolopsis Bell,1863; Hoplitocarcinus Beurlen, 1928; Laeviprosopon Glaess-ner, 1933; Latheticocarcinus Bishop, 1988; LignihomolaCollins, 1997; Prohomola Karasawa, 1992; TithonohomolaGlaessner, 1933; Zygastrocarcinus Bishop, 1983.

Discussion. The family Homolidae is primarilydefined by its lineae homolicae, lateral groovesthat extend the length of the carapace proximal tothe lateral margins (Glaessner 1969:R406). Thelineae aid in carapace separation during moltingand also result in the rapid disarticulation of thecarapace on death. The extra-lineal portions of thecarapace, herein referred to as the lateral flanks,are composed of the lateral margins of the cara-pace and subdorsal regions. Although many rep-

resentatives of the family Homolidae have beenidentified within the fossil record, their relation-ship to extant representatives remains unresolved.Speculation within the literature concerning theaffinity of fossil to extant genera has been tenuousat best (Bishop 1983; Collins 1997), perhaps thesole exception being the relationship of theEocene Dagnaudus pritchardi (Jenkins 1977) andthe extant Dagnaudus petterdi (Grant 1905). Thesystematics of the extant homolids has beenlargely the result of work by Guinot (1995) andGuinot and Richer deForges (1981, 1995).

Genus Latheticocarcinus Bishop, 1988

Type species. Latheticocarcinus shapiroi Bishop, 1988, by orig-inal designation.

Included species. Latheticocarcinus adelphinus (Collins andRasmussen, 1992) as Eohomola; L. affinis (Jakobsen andCollins, 1997) as Eohomola; L. atlanticus (Roberts, 1962), asHomolopsis; L. brevis (Collins, Kanie, and Karasawa, 1993), asMetahomola; L. brightoni (Wright and Collins, 1972), as Ho-molopsis; L. centurialis (Bishop, 1992), as Homolopsis; L. dec-linatus (Collins, Fraaye, and Jagt, 1995), as Homolopsis; L.dispar (Roberts, 1962), as Homolopsis; L. ludvigseniSchweitzer, et al.; L. pikeae (Bishop and Brannen, 1992), as Ho-molopsis; L. punctatus (Rathbun, 1917), as Homolopsis; L.schlueteri (Beurlen, 1928), as Homolopsis; L. shapiroi; L.spiniga (Jakobsen and Collins, 1997), as Homolopsis; L. tran-siens (Segerberg, 1900), as Homolopsis.

Latheticocarcinus shapiroi Bishop, 1988Figures 4, 5 and 8.

Latheticocarcinus shapiroi Bishop, 1988:378, fig. 1E-H, J, M;Schweitzer et al. 2004, p. 136.

Hoplitocarcinus shapiroi (Bishop); Collins, 1997: 61.Homola shapiroi (Bishop); Schweitzer 2001:522.

Material examined. YPM 32067, 35231, 53047, 53048, 37329,37332, 37334–37337, 204059 and 207186, dorsal carapaces;YPM 204054, 35229, 204051 and 204044, partial dorsal cara-paces; YPM 204049, 205192, 202263, 204045, 204052 and204378, lateral flanks; and YPM 32437, partial lateral flank.

Localities and stratigraphic position. See Appendix B for spe-cific locality information. Nearly all the specimens of L.shapirio came from concretions collected from the LowerScaphites (Hoploscaphites) nicolleti (Morton, 1842) abun-dance zone (see Waage 1968:64), Little Eagle lithofacies, TrailCity Member of the Fox Hills Formation in Corson and Deweycounties, South Dakota.

Emended description. Dorsal carapace very small, sub-quadrate in outline, longer than wide when width is measuredbetween the lineae homolicae, widest at epibranchial region


posterior to cervical groove; length measured along medial axisfrom base of rostrum to posterior margin, length to width ratio1.12 to 1.13. Carapace regions moderately well defined. Moltedflanks are one-quarter of carapace width in dorsal view, curv-ing toward axis ventrally. External surface of dorsal carapacefinely granular. Anterior and posterior margins weaklyrimmed; lineae homolicae well developed, sinuous in outline;lateral margins of carapace convex; carapace strongly vaultedtransversely and weakly vaulted longitudinally in anterior one-quarter. Frontal area broad. Rostrum simple, well developed,triangular in outline, axially sulcate and downturned; tip bro-ken so that nature of rostrum termination is unknown. Smallsupraorbital spines present on anteromarginal rim, approxi-mately one-third maximum carapace width from medial axis.Upper orbital margin narrowly rimmed, orbital area not visi-ble; extraorbital area large beyond lineae homolicae, smooth,distally widening, triangular cavity; bounded anteriorly by an-teriorly projecting, small, inner-suborbital spine (broken).

Large anterolaterally projecting, blunt, outer-suborbital spine,distally bifurcating and abruptly terminated. Extraorbital areabounded posteriorly by subhepatic spines, just anterior to cer-vical groove. Anterolateral margin angular, point of inflectiondefined by subhepatic spine; subhepatic spine coarsely granu-lar, well-defined anteriorly by subhepatic groove and posteri-orly by continuation of cervical groove. Lateral flank inflated inepibranchial area, coarsely granular. Posterolateral margincoarsely granular and weakly convex. Posteriormost portion offlank missing, margin presumed to be obliquely directed to-ward medial axis. Posterior margin approximately 60% ofmaximum carapace width, concave; marginal rim mostly pre-sent, distinct laterally and indistinct axially. Epigastric and pro-togastric regions weakly differentiated, epigastric regionstriangular, widening anteriorly, inflated, weakly defined later-ally. Large protogastric regions well defined as elliptical innerlobe, and outer oblanceolate lobe parallel to medial axis sepa-rated by a shallow depression oriented parallel to linea. Meso-


Figure 4. Latheticocarcinus shapiroi Bishop. 1. Dorsal carapace, YPM 53047. 2. Dorsal carapace, YPM 53048.3. Dorsal carapace, YPM 36067. 4. Dorsal carapace, YPM 37336. 5. Left flank, YPM 205192. 6. Posterior part ofdorsal carapace, YPM 35231. 7. Anterior part of dorsal carapace, YPM 35229. 8. Dorsal carapace, YPM 207186.9. Dorsal carapace, YPM 37335. Scale bars equal 1 cm.

gastric region well defined; long anterior process, process ter-minating anteriorly just before maximum inflation of epigas-tric region; differentiated from triangular posteriorly wideningportion by weak transverse sulcus; posteriormost portion con-taining three elevations; one central elevation followed by twoelongate elevations axially. Metagastric region widest anteri-orly, converging posteriorly, comprised of two transversely ori-ented, elongate swellings. Urogastric region narrow anddepressed. Cardiac region triangular, inflated, directed posteri-orly. Intestinal region short, strongly depressed, narrowingposteriorly. Hepatic regions rectangular in outline, orientedoblique to longitudinal axis of carapace, with two oblongswellings proximal to and aligned with linea. Small swellingpresent at intersection of protogastric–mesogastric groove andcervical groove, terminating apically in three small tubercles.Cervical groove deeply incised and discontinuous across me-dial axis, originating axially between mesogastric and metagas-tric regions, continuing anteriorly in convex forward arc,extending around subhepatic region on flanks and ventrallymeeting subhepatic groove. Epibranchial and mesobranchialregions lying between cervical and branchiocardiac grooves.Epibranchial regions rectangular, inflated, with small swellingproximal to linea, small tubercule at level of widest portion ofmesogastric region.

Discussion. The dorsal carapace morphology ofthe specimens examined conforms to the definitionof L. shapiroi as stated by Bishop (1988), and to thegenus Latheticocarcinus Bishop, 1988, as emended

by Schweitzer et al. 2004. The length to width ratioof 1.13 of the new material is identical to measure-ments taken from the published photograph of thetype specimen.Although Bishop reported a ratio of1.21, the discrepancy is probably due to dissimilarmeasurement criteria. The extralineal lateral flanksdiscovered within the concretion material can rea-sonably be identified as L. shapiroi by the correla-tion of the cervical groove, branchiocardiacgroove, and size and relative positions of inflationson the flanks to that of the carapace.

Bishop (1988) placed L. shapiroi within theDakoticancroidea Rathbun, 1917, postulating thatL. shapiroi had descended from Dakoticancer.However, the Dakoticancroidea are not closely re-lated to the Homoloidea, as they lack the lineaehomolicae characteristic of the Homoloidea.Bishop apparently interpreted the specimen hestudied to be an entire carapace, rather than a dor-sal carapace bounded by lineae. Collins (1997:61),in his review of the Homolidae, identified L.shapiroi as a homolid, noting a strong resemblancein carapace morphology to Hoplitocarcinus punc-tatus, and therefore synonymized Latheticocarci-nus with Hoplitocarcinus. Further, he suggested

Figure 5. Reconstruction of Latheticocarcinus shapiroi, showing location of dorsal carapace regions (YPM53048) and position of extralineal flanks (based on YPM 205192). Abbreviations: C, cervical groove; G, proto-gastric region; H, hepatic region; MR, metabranchial ridge; IS, inner suborbital spine; OS, outer suborbitalspine; SH, subhepatic spine.


the two species may be synonymous. Schweitzer(2001) reassessed the Homolidae, placing severalspecies previously assigned to separate generawithin Homola Leach, 1815, and also syn-onymized Latheticocarcinus, Eohomola, Meta-

homola and Hoplitocarcinus with Homola. Shealso referred H. punctatus to Latheticocarcinus.Subsequently, Schweitzer et al. (2004) emendedthe previous diagnosis, reinstating Hoplitocarci-nus and Latheticocarcinus as valid genera. Eoho-


Figure 6. Isolated pereiopod elements and Raninella oaheensis Bishop. 1. Outer surface of merus? of Type 3pereiopod, YPM 205194. 2, 3. Outer and inner surface of carpus?, YPM 204062. 4. Partial mold of dorsal cara-pace of R. oaheensis, YPM 36066. 5. Indeterminate fragment of decapod, YPM 36069. 6. Outer surface of leftcheliped of R. oaheensis, with distal part of propodus and complete dactylus, YPM 36065. 7. Outer surface ofleft propodus of Type 2 pereiopod, YPM 37333. 8. Inner surface of left propodus of Type 2 claw, broken prox-imally to show mold of outer surface, YPM 37331. Scale bars equal 1 cm.

mola and Metahomola were referred to Lathetic-ocarcinus as subjective junior synonyms. We con-cur, and therefore recognize the above fossilhomolid genera as valid.

Examination of the material from the YalePeabody Museum collection yielded more than 20specimens identified as L. shapiroi (see AppendixB). The lateral flanks and appendages of the Ho-molidae are typically not known from the fossilrecord. Therefore, the discovery of the lateralflanks of L. shapiroi provides a significant addi-tion to our understanding of the fossil Homoli-dae. The systematic paleontology of theHomolidae has been difficult because of the lackof complete specimens with external carapacemorphology similar to extant forms. Many of thediagnostic characters of extant homolids arefound on portions of the animal that are rarelypreserved, such as the lateral flanks, maxillipeds,pereiopods and internal anatomy.

Methods. Digital images manipulated in AdobePhotoshop® were used in the reconstruction ofthe carapace of Latheticocarcinus shapiroi to sub-stitute missing portions of the carapace with thosefrom other specimens, with proportional scalingof carapace segments from specimens of slightlydifferent sizes. A complete dorsal carapace, YPM53048, and a left-side flank, YPM 205192, wereused. Although several flank fragments werefound within the concretion material, only onewas complete enough to use in the reconstruction.The carapace and lateral flanks were prepared forphotographing using the standard technique ofdarkening the specimen with India ink and thenwhitening the specimen with ammonium chlo-ride. Photographs were then imported into Pho-toshop®, where they were converted to grayscaleimages, and the brightness and contrast adjusted.The images of the lateral flank were proportion-ately scaled to match the size of the carapace tothat of the flank. Proportionate scaling of the leftflank to the carapace accurately aligned the flankwith the dorsal carapace. Once the flank was ap-propriately scaled, a right-side flank was producedby copying and then horizontally inverting theimage of the left flank. The resulting compositeimage (see Figure 5) was printed and traced in ink.This preliminary ink drawing was scanned, its in-dividual features stippled using Photoshop®’sbrush tool on a fine setting, and final corrections

and labels added. The combination of traditionalink and digital illustration techniques is an effi-cient way to produce accurate drawings, and al-though the composite image does not account forsubtle variation between individuals, it allows fora rapid and accurate reconstruction of an organ-ism from incomplete material.

Superfamily Raninoidea de Haan, 1839Family Raninidae de Haan, 1839

Genus Raninella A. Milne Edwards, 1862

Type species. Raninella trigeri A. Milne Edwards, 1862, byoriginal designation.

Included species. Raninella carlilensis Feldmann and Maxey,1980; R. eocenica Rathbun, 1935; R. libyca Van Straelen, 1935;R. mucronata Rathbun, 1935; R. oaheensis Bishop, 1978; R.quadrispinosus (Collins, Fraaye and Jagt, 1995), as Rani-noides?; R. trechmanni (Withers, 1927), as Ranina; R. trigeriA. Milne Edwards, 1862; R. tridens Roberts, 1962.

Raninella oaheensis Bishop, 1978Figure 6, 4 and 6.

Raninella oaheensis Bishop, 1978:615, pl. 1, figs 7–11, pl. 2,figs. 1–19; Tucker et al. 1987:284.

Material examined. YPM 36065, consisting of a nearly com-plete left chelipeds, and YPM 36066, a partial carapace lackingthe front.

Localities and stratigraphic position. See Appendix A for spe-cific locality information. YPM 36065 was collected from theTimber Lake Member of the Fox Hills Formation at localityA1138 of Waage, Corson County, South Dakota. YPM 36066was collected from the Trail City Member of the Fox Hills For-mation at locality A0313 of Waage, Corson County, SouthDakota. Bishop (1978:615) reported the species from severallocalities in South Dakota along the Missouri River and from asingle specimen collected in southeastern Montana. Tucker etal. (1987) recognized the species in southwestern NorthDakota.

Description of material. Carapace elongate, 11.9 mm long (al-though the front is broken), and 6.1 mm wide. Greatest widthof the specimen attained in advance of midlength. In outline,anterolateral margin appears smooth and straight; posterolat-eral margin smooth and weakly convex. Posterior margin ap-pears slightly convex. Cuticle exfoliated; mold of interior ofcarapace generally smooth with faint impression of branchio-cardiac grooves and axial ridge. Anterolateral and lateral spineseither absent or strongly reduced.

Weakly convex outer surface of left cheliped exposes dis-tal part of hand, fixed finger, and dactylus. Surfaces generallysmooth with no indication of spines on upper or lower mar-gins. Fixed finger deflected at angle of approximately 60º tolong axis of broad hand, nearly straight proximally and


strongly hooked at distal termination. One moderately largedenticle situated at midlength on occlusal surface. Dactylus hasweakly arched upper surface and nearly straight occlusal sur-face.

Discussion. Fossil raninids are not common in theupper midcontinent of North America. In theCretaceous rocks of the region only two specieshave been described: R. oaheensis, from the Cam-panian Pierre Shale of South Dakota and R.carlilensis Feldmann and Maxey, 1980, from theTuronian Carlile Shale of Kansas. Comparison ofthe material from the Fox Hills Formation withthese two species confirms that the material ismost likely referable to R. oaheensis, because thecarapace specimen lies within the size range of thetype series of that genus and the outline of thecarapace is nearly identical to that of the holotype,USNM 173589, deposited in the U. S. NationalMuseum of Natural History. Although the speciesis described as having a lateral and several smalleranterolateral spines, these spines are not clearly ev-ident on moldic specimens. The lateral and an-terolateral spines on R. carlilensis are muchstronger and are evident on moldic specimens.Furthermore, the anterior margin of the latterspecies is much broader than that on the Fox Hillsmaterial. Finally, the morphology of a cheliped

preserved on R. carlilensis is quite different fromthat of Fox Hills specimen YPM 36065. The fixedfinger on R. carlilensis is strongly reduced and ishardly distinguishable from the relatively slenderhand, whereas that on YPM 36065 projects signif-icantly away from the somewhat broader hand.Chelipeds have not been described on R. oaheen-sis, so this record provides significant new infor-mation about the taxon. The strongly deflexedfixed finger and terminal dactylus seen on thisspecimen is typical of raninid claws and, althoughthere is nothing about the claw that would place itwithin a genus unequivocally, it certainly doesconfirm the family placement. Association in thesame formation and the same general geographicarea of the claw with the carapace referable to Ra-ninella provides circumstantial evidence that theclaw is also referable to Raninella oaheensis.

Pereiopods (Position Uncertain)

Discussion. Several isolated appendage elementsare preserved in the Fox Hills Formation concre-tions; however, none are associated with carapacematerial. Thus, it is not possible to describe theiraffinities with certainty. Examination of the pat-terns of ornamentation on the various elements

Figure 7. Isolated pereiopod elements. 1. Outer surface of left merus? of Type 1 pereiopod, YPM 204380.2. Outer surface of broken fragment of Type 1 pereiopod, YPM 202262. 3. Outer surface of badly weathered leftpropodus of Type 1 pereiopod, YPM 202261. 4. Outer surface of merus? of Type 2 pereiopod, YPM 202260.Scale bars equal 1 cm.


suggests that three different morphotypes exist. Allthree morphotypes lie within the same size rangeand all are of a size that could reasonably be as-signed to Latheticocarcinus shapiroi, the mostcommon species in the Fox Hills decapod fauna.The problem of positive identification is exacer-bated by the observation that claw morphology inextant homolids is so variable that there does notseem to be any recognizable pattern (Jenkins 1977;Guinot and Richer de Forges 1981, 1995). Further-more, examination of illustrations of extant taxa,for example, Paromola petterdi (Grant 1905)shows that the spine morphology of the merus,carpus, and propodus of a single individual canhave quite different patterns (Jenkins 1977).Therefore, to avoid possible erroneous interpreta-tion and assignment, it is prudent to describe andillustrate each morphotype and to indicate that,until appendages can be unequivocally associatedwith carapace material, there is no means to assignthe fragments with certainty. See Appendix C forspecific locality information for the isolated claws.

Pereiopod Type 1Figure 7.

Material examined. Five specimens tentatively identified asmeri, YPM 204046, 204050, 204058, 204377 and 204380; onespecimen tentatively identified as a carpus, YPM 204381; andtwo additional specimens, YPM 202261 and 202262.

Localities and stratigraphic position. YPM 204046 and 204058were collected from the Trail City Member of the Fox Hills For-mation at locality A0270 of Waage, Corson County, SouthDakota. YPM 204050, 202261 and 202262 were collected fromthe Trail City Member of the Fox Hills Formation at localityA0644 of Waage, Corson County, South Dakota. YPM 204377,204380 and 204381 were collected from the Trail City Memberof the Fox Hills Formation at locality A0958 of Waage, CorsonCounty, South Dakota.

Description. Specimens identified as meri are about twice aslong as high; the carpus is about 1.5 times as long as high(Table 1). Surfaces densely covered with weakly ovoid granulesarrayed with long axes transverse to long axis of segment; ap-proximately two granules per millimeter.

Pereiopod Type 2Figure 6, 7 and 8; Figure 7, 4.

Material examined. One specimen tentatively identified as amerus, YPM 204043; three propodi, YPM 37331 (inner leftpropodus), 37333 (inner right propodus), 204064 (outer rightsurface); one indeterminate specimen, YPM 202260.

Localities and stratigraphic position. YPM 37331 and 37333were collected from the Trail City Member of the Fox Hills For-

mation at locality A4665 of Waage, Corson County, SouthDakota. YPM 204043 was collected from the Trail City Mem-ber of the Fox Hills Formation at locality A0313 of Waage, Cor-son County, South Dakota. YPM 204064 was collected fromthe Trail City Member of the Fox Hills Formation at localityA0643 of Waage, Corson County, South Dakota.

Description. Merus more than twice as long as high, cylindri-cal. Propodus with bulbous hand, longer than high, fixed fin-ger uniformly tapering, not as long as hand. Surfacesornamented by closely spaced, very fine pustules, about four tosix per millimeter, each about 0.1 mm in diameter; pustuleshave weak preferred orientation in longitudinal rows. A fewsetal pits also present.

Pereiopod Type 3Figure 6, 1–3.

Material examined. YPM 205194, merus? YPM 204042, inde-terminate element; YPM 204062, carpus? YPM 204379, car-pus?

Localities and stratigraphic position. YPM 205194 was col-lected from the Trail City Member of the Fox Hills Formationat locality A0313 of Waage, Corson County, South Dakota.YPM 204042 was collected from the Trail City Member of theFox Hills Formation at locality A0518 of Waage, CorsonCounty, South Dakota. YPM 204062 was collected from theTrail City Member of the Fox Hills Formation at locality A0643of Waage, Corson County, South Dakota. YPM 204379 wascollected from the Trail City Member of the Fox Hills Forma-tion at locality A0296 of Waage, Corson County, South Dakota.

Description. Merus(?) about twice as long as high, ovoid out-line widest at midlength; distal end with swollen, bulbous col-lar bearing two swellings. Carpus about twice as long as high,widening distally. Elements with about three rows of coarsegranules, about nine granules per row, on outer surface sepa-rated by longitudinal depressed, smooth areas.

Taphonomy ofFox Hills Decapods

Decapod fossils are rare (Feldmann and McPher-son 1980) and are generally not preserved under“normal” depositional conditions; that is, for acrab or other decapod to fossilize, it must besomehow protected from transport, abrasion andscavenging (Feldmann and McPherson 1980;Bishop 1981, 1986). The exception to the rule thatonly unusual preservation events result in the fos-silization of decapods is the resilience of the moreheavily calcified components of the decapod cuti-cle. Heavily calcified appendages, such as chelaeand spines, have a higher potential for preserva-tion and are probably the most common compo-nents of the decapod fossil record (Glaessner


1969). Preservation of calcified appendages andmouthparts, with destruction of other hard partsunder normal marine conditions, is supported byexperimental taphonomic work on crabs (Mutelet al. 2004). The high potential for preservation ofheavily calcified skeletal parts is somewhatnegated by the fact that these easily overlookedsmall fragmented parts are not collected and, be-cause they are not taxonomically useful, are ex-cluded from the literature.

The more fragile decapods are preserved in theTrail City Member of the Fox Hills Formation.The Trail City Member is the fine-grained, distalmember of the formation, deposited below thenormal wave base. The fossils are preserved in con-cretions.Only the larger,more durable lobsters andthe burrowing callianassid are found in the TimberLake Member, a coarse-grained, proximal depositthat was probably deposited in a higher energyregime. Fine-grained offshore environments oflow energy and sedimentation are one of the mostcommon environments for decapod preservation(Förster 1985).What makes the Fox Hills preserva-tion unusual is that the same concretions that con-tain decapod material also contain a largemolluscan fauna. Typically, molluscs and decapods

are preserved separately from one another, evenwithin the same stratigraphic unit.

Concretions of the Fox Hills

In many ways, the preservation of the concretionsin the Fox Hills Formation is linked to their na-ture; these will be discussed together. Studies ofconcretions from the Fox Hills Formation havebeen summarized by Feldmann (1972); the con-cretions were first reported by Lewis and Clark in1804 (Thwaites 1905 in Feldmann 1972). Theirorigin and nature have been recorded by severalauthors since that time (Erickson 1974; Carpenteret al. 1988). The diagenetic processes of concretionformation from the Timber Lake Member of theFox Hills Formation in North Dakota have beenstudied by Carpenter and co-workers (1988), butthe sedimentologic conditions that resulted in theconcentration of the organisms found in the con-cretions remains unexplained. Mass-death eventsseem to be the dominant hypothesis to explain theconcentration of faunal remains in layers that ex-tend over broad areas (Waage 1964; Erickson1974).

The concretions range in size from 17 cm to

YPMTaxon catalog number Identification Length Width

Pereiopod Type 1 204046 Merus 11.1 5.9

204050 Merus? 6.4 3.4

204058 Merus? >7.3 3.6

204377 Merus? 4.1 2.3

204380 Merus 11.5 6.1

204381 Carpus? 5.6 3.5

Pereiopod Type 2 37331 Inner surface >3.8 (hand) 2.9 (hand)left propodus 2.3 (finger)

37333 Inner surface >3.6 (hand) 2.6 (hand)right propodus 2.6 (finger)

204043 Merus 5.7 2.6

204064 Outer surface 4.6right propodus 3.5

Pereiopod Type 3 205194 Merus? 5.7 2.8

204062 Carpus? 6.7 3.4

204379 Carpus? 4.4 2.3

Table 1. Measurements, in millimeters, taken on samples of appendage fragments.


1.8 m in diameter (Speden 1970). Many of theconcretions are covered in a soft, calcified jacket orgypsum rind, which in some cases is separatedfrom the core by carbonates or gypsum (Waage1968; Speden 1970). Although the concretions arethe main mode of fossil preservation, most concre-tions are devoid of fossil material (Speden 1970).

PreservationMost of the Fox Hills fauna is preserved in con-cretions (Waage 1964), and the decapods of thisstudy occur in this way. The Iron Lightning Mem-ber and upper Timber Lake Member seem to beexceptions to the concretionary preservation(Speden 1970). The fossils not enclosed withinconcretions or in the margins of concretions areoften crushed (Waage 1964; Speden 1970). The re-lationship to crushed fossils outside concretionssuggests that cementation took place before com-paction of the surrounding sediment. Regardlessof how the concretions formed, the preservationof the enclosed fossils is excellent. Ligaments, color

banding and periostracum occasionally were pre-served (Waage 1964, 1968; Speden 1970), as wereoriginal aragonite of molluscs (Carpenter et al.1988). Scanning electron microscopy (SEM) ob-servation of molluscs from locality A0713 alsoshowed aragonite, which we have confirmed usingX-ray diffraction, although thin sections from thesame sample show local recrystallization of mol-lusc material. The process of X-ray diffraction isdestructive and no sample of the specimen re-mains.

TransportThe fossil assemblages of the Fox Hills Formationshow little sign of transport before burial. Evi-dence for minimal transport includes lack of abra-sion, articulation of bivalves, and the generalabsence of borings or encrustation (Waage 1964;Speden 1970; Feldmann 1972; Carpenter et al.1988), although abraded and fragmented materialis common in the Iron Lightning Member (Spe-den 1970). During the course of this study only

Figure 8. SEM image of a fragment of cuticle from Latheticocarcinus shapiroi Bishop showing the exocuticleexfoliating from the endocuticle (YPM 204054). Note that the nodes are visible on both the exocuticle and en-docuticle surfaces. Scale bar equals 0.5 mm.


two gastropod drill holes were found in pelecypodshells. Some transport must have taken place, asindicated by assemblages of pelecypods with dif-ferent life habits, clustering of individuals of dif-ferent sizes (Speden 1970), and disarticulation ofdecapod material. As with most other studies(Waage 1964; Carpenter et al. 1988), the fossilsseem to be randomly oriented within the deca-pod-containing concretions. The extent of post-mortem transport remains enigmatic.

BioturbationIn their study, Carpenter and co-workers (1988)made important observations on the extent andtype of bioturbation present within the concre-tions. They found that up to 25% of the concre-tions were composed of fecal pellets and burrows(Carpenter et al. 1988). The fecal pellets they de-scribed are of two types: one smaller set is ascribed

to annelids and another set assigned to the ichno-genus Palaxius Brönnimann and Norton, 1960,which is thought to be formed by small crus-taceans. That the pellets are not compacted, cou-pled with the presence of associated burrows,suggests that the burrowers and pellet producerswere responsible for the bioturbation in the pro-toconcretion sediment (Carpenter et al. 1988).From their petrographic study, Carpenter and hisassociates concluded that the burrowing tookplace within one meter of the surface under aero-bic conditions. This bioturbation was also respon-sible for the dissemination of organic materialwithin the protoconcretion area, which helpednucleate concretion formation (Carpenter et al.1988). Preburial bioturbation could explain theapparently random orientation of fossils pre-served within the concretions (Waage 1964;Rhoads et al. 1973; Carpenter et al. 1988). Our ob-

Figure 9. Preserved cuticle and regions of bioturbation in a concretion containing Hoploparia sp., YPM 203898.1. Proximal end of moveable finger. Arrow a points to region of glassy conchoidal fracture typical of this preser-vation type. 2. Photomicrograph of cuticle in plain polarized light (note the well-preserved laminations);b points to exocuticle, c points to truncated laminations at the junction with the matrix. 3. Polished section ofconcretion close to area of claw preservation (note abundant burrows and fecal pellets); d points to aggregated?fecal pellets, e points to burrow. 4. Cuticle in crossed polarized light showing recrystallization of the cuticle; f de-notes pocket of recrystallization under exocuticle, g points to relict laminations in otherwise recrystallized area.


servations of the decapod-bearing concretionsalso reveal a high degree of bioturbation in associ-ation with fecal pellets. The presence of fecal pel-lets and burrows suggests that reworking byinfauna is common to concretionary layers withinthe Fox Hills Formation. A polished portion of aconcretion containing a lobster (YPM 203898) re-veals a series of burrows that are lighter in colorcompared to the ground mass, and a series ofprobable aggregated fecal pellets that are darkerthan the surrounding rock (Figure 9, 3). It is note-worthy that concentrations of fecal pellets haveaslo been described from crab-bearing horizons inthe Pierre Shale (Bishop 1977).

Arthropod TaphonomyThe study material consists of dorsal carapacesand claw fragments from lobsters and crabs. Withthe exception of one lobster, most of the decapodmaterial from the Fox Hills is consistent with theburial of molted material. Lack of legs and otherskeletal parts in this case is considered indicative oftransported molted material that was not exposedfor an extended period on the sea floor. Althoughthe evidence is circumstantial, it is consistent withthe criteria typically used to represent molted re-mains (Bishop 1986). Molts or corpses that wereexposed for any significant time would have beenscavenged (Tshudy et al. 1989) or would have de-veloped characteristic signs of decay or abrasion(Mutel et al. 2004).

The Homolidae have lineae on the lateral por-tions of the dorsal carapace that split during themolt (Glaessner 1969). This disarticulation of thedorsal carapace during the molt results in the com-mon occurrence of only isolated dorsal and lateralsections of the carapace, indicating that the cara-pace is most likely a molt rather than a corpse(Glaessner 1969). The homolids recovered in theFox Hills follow this pattern; articulated dorsal andlateral parts of the carapace are not found articu-lated, although both portions have been recoveredin the concretions. Recovery of true molts doesbring into question, but does not refute, the hy-pothesis that the fauna of the Fox Hills is the resultof a rapid mass-death event. The result of minortransport and decay of homo lid corpses and thestructural integrity of the lineae on corpses thathave not undergone a molt have not been studied.It is possible that the dorsal carapace of homolidscould become separated during minor transport

or episodes of bioturbation allowing corpses tomimic molts. Decay of noncalcified or weakly cal-cified points of articulation in arthropods resultsin easily disarticulated reamins. Even mild biotur-bation below the sediment–water interface wouldthen disassociate the material.

The lobster material studied consists of threeclaws and one complete specimen, all preserved inconcretions. The claws could be molted materialthat has become disarticulated from the carapace,or the remains of a scavenged corpse. The claws donot show the signs of decay that would have re-sulted from extended exposure on the sea floor(Mutel et al. 2004); articulation of the movablefinger on the claw fragments also suggests mini-mal time and distance of transport (see Figure 9,1).

Cuticle PreservationAs observed in the molluscan material, the preser-vation of the arthropod cuticle varies. Scarcity ofmaterial that could be destructively sampled hasmade it difficult to assess the range of preservationvariability. Observation by SEM of a single ho-molid specimen reveals that the exocuticle and atleast part of the endocuticle are present (see Figure8). Laminations in the cuticle were not observedin the weathered (on the outcrop) sample that wassubjected to SEM analysis. Laminations were re-vealed under the light microscope on anotherspecimen. As is commonly observed, the cuticlehas parted along its internal laminations (Waughet al. 2004). Often, structures that seem to be onthe surface of decapod fossils are not features pre-sent on the outer surface, but reside within the in-ternal laminations of the cuticle. With SEM thesefeatures can be seen both on and under the pre-sumed exocuticle; this implies that fine-scale ex-ternal morphology is preserved and is not anartifact of exfoliation of cuticle layers.

The preservation of the lobster cuticle is ex-ceptional. Outwardly the cuticle looks black andglassy with conchoidal fracture (see Figure 9, 1). Inthin section the exocuticle, endocuticle, porecanals and tegumental canals are clearly preserved(see Figure 9, 2). X-ray diffraction analysis of YPM36068 (an intermediate arm fragment) shows thecuticle to be composed of apatite, but the smallsample size prevented identification of the exactmineral phase. Although the cuticle preservationis excellent, it seems to have gone though a phase


of recrystallization that has eroded the innermostpart of the endocuticle (see Figure 9, 4). The ex-tent of endocuticle cuticle loss is unclear as arthro-pods reabsorb some of their inner endocuticlebefore molting.

Summary

Examination of many decapod crustacean speci-mens from the Fox Hills Formation has increasedthe known fauna from two brachyurans and oneanomuran to more than five taxa, with the addi-tion of another brachyuran and one macruran.Additionally, three pereiopod types suggest thateven more taxa were present. The specimens aregenerally well preserved and, in the cases studied,the microstructure of the cuticle is well preserved.The quality of preservation results from the de-capods being preserved within concretions, typi-cally in association with many well-preservedmolluscs. Because the curent study was based onspecimens collected and recognized over a periodof nearly 50 years, and because most of the speci-mens are tiny and inconspicuous, we anticipatethat additional collecting will yield new decapodsat a very low rate.

Acknowledgments

This study would not have been possible had itnot been for the painstaking examination of bitsof concretions, collected by K. Waage and I. Spe-den, among others. Some of the specimens wererecognized by them and others by C. MacClintock(Peabody Museum of Natural History, Yale Uni-versity). MacClintock and S. Butts (Peabody Mu-seum of Natural History, Yale University) assistedgreatly in the loan of material. The Hoplopariaspecimen from North Dakota was collected by D.Hanson (Bismarck, North Dakota) and the loanof it and other specimens was facilitated by J.Hoganson (North Dakota State Geological Sur-vey, Bismarck). This work originated as a classproject in paleoceanography, and students in thatclass, including C. Klepper, K. Traugh and M.Wilsbacher, contributed important backgroundliterature research and a summary to the effort.The manuscript was carefully read and substan-tially improved by C. Schweitzer (Kent State Uni-versity). Finally, reviews by C. MacClintock, L. Gall(Peabody Museum of Natural History, Yale Uni-

versity), S. Butts, and G. A. Bishop (South DakotaSchool of Mines and Technology) substantiallyimproved the final product.

Received 29 March 2005; revised and accepted27 March 2006.


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Appendix A

Locality information for Raninella oaheensis, Hoploparia sp. and Callichirus waagei n. sp.

YPM Section,County, catalog township,

Taxon state Locality number Quadrangle range

Hoploparia sp. Dewey A0673 203892 Parade S1/2, SW1/4, SE1/4,County, SD NW NW1/4, sec 32,

T 15 N, R 24 E;N1/2, NW1/4,SW1/4, sec 32,T 15 N, R 24 E

Hoploparia sp. Niobrara D6293 203897 Redbird NW1/4, NW1/4,County, WY sec 20, T 62 N,

R 37 W; NE corner,sec 19, T 62 N,R 37 W; SE corner,sec 18, T 62 N,R 37 W

Hoploparia sp. Niobrara A4754 203898 Redbird S1/2, S1/2, sec 18,County, WY T 62 W, R 37 N

Callichirus waagei Corson A0370 35098 Black Horse NE N1/2, NW1/4,County, SD NE SE1/4, sec 31,

T 21 N, R 23 E

Raninella oaheensis Corson A0313 36066 Wakpala NW1/4, SW1/4,County, SD NW sec 15, T 20 N,

R 28 E; SW corner,NW1/4, sec 15,T 20 N, R 28 E

Raninella oaheensis Corson A1138 36065 Wakpala Center, N1/2, SE1/4,County, SD SW sec 31, T 19 N, R 28 E


Appendix B

Locality information for Latheticocaricinus shapiroi specimens.

YPM Section,catalog township,

County, state Locality number Quadrangle range

Corson County, SD A0285 35231 Bullhead S1/2, NW1/4, sec 24, T 21 N, R 24 E

A0296 204378 Bullhead S1/2, NW1/4, sec 24, T 21 N, R 24 E

A0313 205192 Wakpala NW NW1/4, SW1/4, sec 15, T 20 N,R 28 E; SW corner, NW1/4,sec 15, T 20 N, R 28 E

A0272 204045 Little Eagle Center, E1/2, SE1/4, sec 5,T 20 N, R 27 E

A0549 204044 Little Eagle Center, N1/2, N1/2, sec 8, T 20 N,R 27 E; Center, S1/2, S1/2, sec 5,T 20 N, R 27 E

A0642 37334 Little Eagle NE corner, sec 7, T 20 N, R 27 E;SE corner, sec 6, T 20 N, R 27 E









A4665 37332 Little Eagle Center, E1/2, SE1/4,sec 5, T 20 N, R 27 E

A4665 53047 Little Eagle Center, E1/2, SE1/4,sec 5, T 20 N, R 27 E

A4659 35229 Little Eagle SE1/4, NE1/4, NE1/4,sec 8, T 20 N, R 27 E

Dewey County, SD A0209 204054 Whitehorse NW corner, SW1/4,sec 30, T 16 N, R 26 E

A0209 36067 Whitehorse NW corner, SW1/4,sec 30, T 16 N, R 26 E

A0713 32437 Whitehorse Center, N1/2, N1/2,sec 17, T 16 N, R 26 E





Appendix C

Locality information for pereiopod specimens

YPM Section,County, catalog township,

Taxon state Locality number Quadrangle range

Pereiopod Type 1 Corson A0270 204046 Little Eagle E1/2, SE1/4, sec 5,County, SD T 20 N, R 27 E

Corson A0270 204058 Little Eagle E1/2, SE1/4, sec 5,County, SD T 20 N, R 27 E

Corson A0644 204050 Little Eagle NE1/4, sec 7, T 20 N,County, SD R 27 E; SE corner,

sec 6, T 20 N, R 27 E


sec 6, T 20 N, R 27 E


sec 6, T 20 N, R 27 E

Corson A0958 204377 Little Eagle NE1/4, sec 7,County, SD T 20 N,R 27 E



Pereiopod Type 2 Corson A0313 204043 Wakpala NW NW1/4, SW1/4,County, SD sec 15, T 20 N, R 28 E;

SW corner, NW1/4,sec 15, T 20 N, R 28 E

Corson A0643 204064 Little Eagle NE corner, sec 7,County, SD T 20 N, R 27 E;

SE corner, sec 6,T 20 N, R 27 E

Corson A4665 37331 Little Eagle Center, E1/2, SE1/4,County, SD sec 5, T 20 N, R 27 E

Corson A4665 37333 Little Eagle Center, E1/2, SE1/4,County, SD sec 5, T 20 N, R 27 E

Corson A0277 202260 Bullhead S1/2, NW1/4,County, SD sec 24, T 21 N, R 24E

Pereiopod Type 3 Corson A0296 204379 Bullhead S1/2, NW1/4,County, SD sec 24, T 21 N, R 24E

Corson A0313 205194 Wakpala NW NW1/4, SW1/4,County, SD sec 15, T 20 N, R 28 E

Corson A0518 204042 Miscol NE SE1/4, SW1/4, SW1/4,County, SD sec 14, T 20 N, R 25 E

Corson A0643 204062 Little Eagle NE corner, sec 7, T 20 N,County, SD R 27 E; SE corner,

sec 6,T 20 N, R 27 E


decapod crustaceans from the maastrichtian fox hills formation

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