www.elsevier.com/locate/revpalbo

Review of Palaeobotany and Pal

Angiosperm leaves from the Kachaike Formation, Lower

Cretaceous of Patagonia, Argentina

Ruben Cuneoa,*, Marıa A. Gandolfob

aMEF, Museo Egidio Feruglio, Trelew, ArgentinabLH Bailey Hortorium, Cornell University, Ithaca, USA

Received 28 July 2004; received in revised form 6 April 2005; accepted 15 April 2005

Abstract

Several angiosperm leaf morphotypes are studied for the first time from the late early Cretaceous Kachaike Formation of

southern Argentina. The angiosperm component of the flora is totally overlapped by other non-angiosperm groups such as

conifers and ferns, which dominate in number of taxa and specimens the plant assemblage. Two new genera, Kachaikenia

and Thorphyllum, a new species Rogersia australis, and four unnamed leaf morphotypes represent the angiosperm

component of the Kachaike flora. All of them show primitive morphological traits such as microphyllous leaves with entire

unlobed margins, pinnate brochidodromous/camptodromous venation patterns with irregular intercostal areas, and relatively

disorganized higher venation orders. Comparisons are made with coeval regional and extra-regional floras in order to

establish a proper context assessing for a possible angiosperm morphological trend in the Cretaceous of southern South

America.

D 2005 Elsevier B.V. All rights reserved.

Keywords: angiosperms; morphotype leaves, Lower Cretaceous; Patagonia; paleofloristics; biostratigraphy

1. Introduction

The record of angiosperm remains from Lower

Cretaceous deposits in Argentina, and Gondwana in

general, has been scarce and sporadic. Interestingly,

one of the first mentions is by Halle (1913) who

0034-6667/$ - see front matter D 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.revpalbo.2005.04.003

* Corresponding author.

E-mail addresses: rcuneo@mef.org.ar (R. Cuneo),

mag4@cornell.edu (M.A. Gandolfo).

described a few fragmentary, unidentifiable angio-

sperm leaf remains from beds that were later incor-

porated into the Kachaike Formation. This material

came from a site located a few kilometers north of

the Arroyo Caballo Muerto (ACM) Creek (Fig. 1),

the source of material for the present study. Rebassa

(1982) also indicated the presence of at least two

types of angiosperm leaves from the same plant

horizon we describe in this contribution. In the

older Baquero Formation (currently grouped, late

Barremian–middle Aptian), better preserved remains

ynology 136 (2005) 29–47

Fig. 1. Location map of the ACM Creek, in southern Argentina.

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–4730

have been described by Romero and Archangelsky

(1986), Passalıa and Cladera (2003) and Passalıa et

al. (2003). Coeval late early Cretaceous (Barremian–

Aptian) or earliest late Cretaceous (Albian–early

Cenomanian) angiosperm leaves from the rest of

Gondwana are patchily known from Brazil (Mohr

and Friis, 2000), Colombia (Pons, 1988), Australia

(Douglas, 1965; Drinnan and Chambers, 1986; Tay-

lor and Hickey, 1990; McLoughlin et al., 1995; Pole,

1999, 2000), New Zealand (Pole, 1992; Parrish et

al., 1998), and Antarctica (Cantrill and Nichols,

1996).

In contrast, the record of angiosperm pollen in

southern South America is more substantial, span-

ning the Barremian through the Albian in several

geological units. This record shows a constant in-

crease in diversity from forms of Clavatipollenites

type (including pollen preserved in situ within

anthers; Archangelsky and Taylor, 1993), to the

classical late early Cretaceous Afropollis or/and

Asteropollis assemblages (Vallati, 1995; Llorenz,

2003). A similar pattern can also be traced in

Antarctica and Australia (Dettmann, 1994; Dettman

and Thomson, 1987; Burger, 1993). The Kachaike

microflora shows an interesting increase in pollen

diversity when compared with pollen from earlier

deposits, such as that from the Baquero Group

(Llorenz, personal communication).

Thus, it is possible that the same changes in diver-

sity patterns indicated by the pollen record are also

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–47 31

present in angiosperm leaf assemblages. A recent

approach on this subject (Archangelsky et al., 2004)

suggests that this is possible, at least for the Patago-

nian region. This contribution, as well as forthcoming

studies, is focused on identifying possible patterns of

morphological change over time by which a clearer

scenario for angiosperm evolution can be detected in

southern Argentina during the Cretaceous period. This

pattern, to some extent, has already been envisaged

for Antarctica (Cantrill and Poole, 2002) and the data

Fig. 2. Stratigraphical section of the Kachaike Formation at ACM Creek. N

and the upper delta plain (mouth bars, distributary channels and distributary

upper delta plain dominated by terrestrial-fresh water facies.

from southern South America will provide additional

information in order to better understand the angio-

sperm radiation in southern high latitudes during the

Cretaceous.

2. Materials and methods

The fossil remains studied here are mostly par-

tially fragmentary leaf impressions; some of them,

ote deltaic deposits of the lower delta plain (prodelta and delta front)

bays). The plant horizon is associated with the uppermost part of the

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–4732

however, are preserved in their entirety indicating a

low degree of transport prior to deposition and

suggesting some taphonomical bias. Most of the

leaf morphotypes are represented by a few speci-

mens while others are more abundant, indicating a

different degree of importance in the taphocoenosis.

Even though angiosperms correspond to a third of

the total number of taxa, they are a minor compo-

nent in terms of counted specimens, representing

only 6% of the plant assemblage. The taphocoenosis

is dominated by ferns (79%) of matoniaceous

(Nathorstia alata Halle), osmundaceous (Cladophle-

bis spp.), and dicksoniaceous (Coniopteris sp.) alli-

ance; conifers correspond to the remaining 15% of the

plant assemblage being represented by twigs and seed

cones of taxodiaceous or cheirolepideaceous affinities

(Athrotaxites, Brachyphyllum).

The angiosperm leaf impressions were described

following the Manual of Leaf Architecture Group

(1999) by the Leaf Architectural Working Group;

descriptions are focused on general morphology

(outline, size, margins) and venation patterns.

Identification of the material studied as angiosper-

mous (dicotyledonous) is primarily based on the

presence of venation patterns clearly showing dif-

ferent orders of veins as indicated by vein distri-

bution and thickness. Taxonomic identifications of

leaf morphotypes are considered entirely artificial

and no systematic or phylogenetic assignments are

implied.

Specimens were observed using a stereomicro-

scope and several morphotypes were reconstructed

using a camera lucida. Photographs were obtained

using a Canon digital camera and then printed with

a Tektronik laser printer. All the materials are stored

at the Paleobotanical collection of the Museo

Paleontologico Egidio Feruglio under the initials

MPEF-Pb-Mz.

3. Geology and age

The Kachaike Formation outcrops on the western

side of the Santa Cruz province in southern Pata-

gonia (Fig. 1). This unit has been recognized since

the beginning of the last century, and corresponds to

littoral/paralic deposits that accumulated during

a regression phase in the Austral Basin (Arbe,

2002). In particular, the section at ACM Creek,

which bears the fossil plant assemblage, is repre-

sented by a series of deltaic cycles, most of them

tide-dominated (Rebassa, 1982). The last of these

cycles (Fig. 2) shows a more conspicuous terrestrial

influence that favors the preservation of fossil

plants. This part of the sequence has been inter-

preted as a delta plain with fluvial dominance that

allows the formation of interdistributary bays less

influenced by tides and whose sediments incorpo-

rate higher proportions of plant remains (Rebassa,

1982; Arbe, 2002).

The age of the Kachaike Formation has been

interpreted from different sources. Most of the se-

quence includes rich palynological assemblages,

both terrestrial and marine. Rebassa (1982) and

Baldoni et al. (2001) have indicated a late Aptian

to early Albian age based on the terrestrial palyno-

logical content. To some extent, this age has been

supported by the presence of ammonite faunas

occurring in the same unit but at a different locality,

and assigned to the Sanmartinoceras patagonica

Zone, whose relative age is late Aptian (Aguirre

Urreta, 2002). More recently, Guler and Archan-

gelsky (2002) suggested an age varying from the

late Barremian through the early Cenomanian based

on phytoplankton assemblages recorded from the

lower and middle parts of the same sequence at

ACM Creek. Further and more detailed studies,

including radiometric dating of volcanic intercala-

tions present in the uppermost part of the sequence,

will be required to settle a finer interpretation of the

formation’s age.

4. Systematic descriptions

Kachaikenia Cuneo et Gandolfo gen. nov.

Type: Kachaikenia compuesta Cuneo et Gandolfo

gen. sp.

Diagnosis: Pinnately compound leaf with alternate

pairs of ovate leaflets. Leaflets with asymmetrical

acute bases and apexes. Margin entire and unlobed.

First vein pinnate; secondary veins craspedodromous

with straight course. Intersecondary veins weak. Third

veins (highest order) random reticulate. Polygonal

areoles well-developed. Fimbrial ultimate marginal

venation.

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–47 33

Kachaikenia compuesta Cuneo et Gandolfo sp. nov.

(Plates I, II; Fig. 3G.)

Diagnosis: Leaves pinnately compound, 6 cm long

and 4 cm wide. Leaflets in alternate pairs (4 or 5),

microphyllous, ovate in shape when fully developed,

with asymmetrical bases; up to 5 cm long and 0.9 cm

wide. Base acute, concave–convex, apex acute to

obtuse. Margin entire and unlobed in basal leaflets

to pinnately lobed in apical leaflets. First vein catego-

ry pinnate. Second vein category craspedodromous;

veins emerging at an acute angle, with straight course,

reaching or not the marginal vein. Secondary veins

spaced irregularly, with increasing space towards the

base. Intersecondary veins weak. Third vein category

(highest) random reticulate, exmedially ramified;

angle to primaries acute to obtuse (inconsistent). Are-

oles well-developed, 3 to 5 or more sided. Ultimate

marginal venation clearly fimbrial.

Repository: Paleobotanical Collection, Museo Paleon-

tologico Egidio Feruglio MPEF-Pb.

Holotype: MPEF-Pb-Mz 1107.

Paratypes: MPEB-Pb-Mz 1111, 1116.

Type locality: Arroyo Caballo Muerto Creek, San

Martin Lake area, western Santa Cruz province,

Argentina.

Horizon: Uppermost part of the Kachaike Formation

at ACM Creek.

Derivatio nominis: Kachaikenia: after the Kachaike

Formation; compuesta refers to the compound char-

acter of the leaf.

Studied material: MPEF Pb-Mz 1106, 1107 A-B,

1108, 1109, 1110, 1111, 1112A-B, 1113, 1114 A-B,

1115 A-B 1116, 1117, 1118, 1119, 1120, 1121, 1122,

1123, 1124, 1125, 1130, 1131, 1132.

Description: This is the most common and abundant

angiosperm leaf morphotype found at the ACM Creek

locality. Larger isolated leaflets (Plate II, 5) provide

additional morphological features. The length of the

most developed basal leaflets vary from 2 to 5 cm

long and 0.7 to 0.9 cm wide (L /W ratio= from 2.8–5.5

to 1). They show a higher length/width ratio when

mature, indicating a strong elongation. This morpho-

type is characterized by mostly pinnately compound

leaves (odd-pinnate) with 4 or 5 pairs of sub-opposite

to alternate leaflets of irregular variable shape (Plate I,

1 and 2; Plate II, 2). The leaflet bases are decurrent on

the catadromic side which, to some extent, slightly

sheaths the main axis, while the anadromic margin is

sharply constricted (Plate I, 3). The basal asymmetry

is observed even in fully developed leaflets (Plate I,

1–3; Plate II, 2). Leaflet bases acute and concave–

convex, while apexes are acute in basal leaflets or

obtuse, straight or rounded, in apical leaflets. Basal

leaflets may also develop a very short marginal peti-

olule while apical leaflets are inserted along the whole

base.

The midvein is only well-developed in basal leaf-

lets and become close to the anadromic side on middle

and upper leaflets (Plate II, 1 and 2), making a gentle

arch, while in the lower leaflets it is slightly displaced

toward the catadromic side (Plate I, 3). On apical

leaflets, the main vein enters basally towards the

apex (Plate II, 1 and 2). The secondary veins arise

at acute angles that vary from 308 in the basal part up

to 458 in the upper part, and mostly join the marginal

vein (Plate II, Fig. 1). In a few cases, they fork before

joining the marginal vein or slightly curve toward the

apex. Third order veins develop polygonal areoles but

no veinlets are seen.

Some of the specimens described could represent

different ontogenetic stages in the development of a

primitive compound leaf. For instance, the specimens

illustrated in Plate I (1 and 4) show a less developed

leaf than those in Plate I (2) and Plate II (2), partic-

ularly in the type and morphology of their apical

leaflets and basal insertions. Besides, some specimens

show possible abnormal development of leaflets

(Plate I, 1).

Comparisons: Single leaflets in our material resemble

those of the genus Eucalyptophyllum Fontaine (1889),

especially in the very peculiar venation pattern,

including the presence of a marginal vein and ter-

tiary vein meshes of polygonal (subrhombic) shape.

The general shape of the leaves is also quite similar,

but the Potomac leaves are much bigger, probably

double the size of the Kachaike ones. On these

grounds, it is possible that Eucalyptophyllum repre-

sents isolated leaflets of Kachaikenia, which is

erected as a compound leaf. Eucalyptophyllum was

originally defined as a monospecific genus (E.

oblongifolium Fontaine) found in the classical Fre-

dericksburg locality of the Potomac Group. This

locality has been biostratigraphically associated to

the palynological Zone I, which age was reported as

late Aptian to early Albian (Hickey and Doyle,

1977). The genus includes a second possible species

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–4734

(Eucalytophyllum sp.) reported from the Middle

Albian Winthrop flora in the Rocky Mountains

(Crabtree, 1987).

Asiatifolium Sun, Guo et Zheng (Sun and Dilcher,

2002) is another genus of compound leaves known

from the early Cretaceous of China. It shares with

Kachaikenia the presence of a sub-marginal vein and

leaflets with asymmetrical bases. However, leaflets

are oblanceolate and opposite in Asiatifolium while

in Kachaikenia they are typically ovate, sub-opposite

to alternate, and do not possess a well-developed

petiolule.

Sapindopsis Fontaine (1889) is also a morpho-

genus of compound leaves described from the classi-

cal Fredericksburg locality of the Potomac Group. It

differs from Kachaikenia by having elliptic leaflets

mostly opposite in pairs, basal leaflets shortly petioled

and a venation pattern with clearly defined intercostal

areas, intersecondary veins, and no intramarginal vein.

Dilcher and Basson (1990) and Huang and Dilcher

(1994) illustrate several types of Sapindopsis which,

in all cases, include compound leaves with only two

or less pairs of opposite petiolate leaflets. In the case

of S. variabilis Fontaine (apparently the most primi-

tive form according to Huang and Dilcher, 1994)

leaflets are inserted by their entire and decurrent

bases as in upper leaflets of Kachaikenia.

Summarizing, Kachaikenia seems to represent a

definitely highly primitive angiosperm compound

leaf whose morphological characters, in particular

shape, outline and venation pattern, are irregularly

Plate I. Kachaikenia compuesta Cuneo et Gandolfo gen. et sp. nov. Scale

1. Paratype (MPEF-Pb-Mz 1116). Compound leaf showing early o

apical and basal leaflets.

2. Paratype (MPEF-Pb-Mz 1111). Compound leaf showing a more

3. Holotype (MPEF-Pb-Mz 1107B). Compound leaf with basal le

4. MPEF-Pb-Mz 1117. Apical part of a compound leaf showing th

Plate II. Kachaikenia compuesta Cuneo et Gandolfo gen. et sp. nov

1. MPEF-Pb-Mz 1106. Early development of apical leaflets.

2. MPEF-Pb-Mz 1130. Compound leaf showing the venation patte

3. Holotype (MPEF-Pb-Mz 1107B). Leaflet venation pattern show

4. MPEF-Pb-Mz 1115A. Apical part of a compound leaf showing

5. MPEF-Pb-Mz 1125. Isolated leaflet showing the venation patte

variable and cannot be recognized in any modern

family.

Thorphyllum Cuneo et Gandolfo gen. nov.

Type: Thorphyllum patagonica Cuneo et Gandolfo

gen. sp.

Diagnosis: Simple leaves with marginal petioles.

Ovate symmetrical lamina; base acute decurrent and

apex acute. Margin entire, unlobed. First vein pinnate

and secondaries brochidodromous. Intercostal areas

well-developed and occupying most of the midvein-

margin space. Third veins random reticulate and sin-

uous. Fourth vein category regular polygonal reticu-

late. Polygonal areoles well-developed. Ultimate

marginal venation looped.

Thorphyllum patagonica Cuneo et Gandolfo sp. nov.

(Plate III, Figs. 1, 2, 3; Fig. 3E.)

Diagnosis: Simple, notophyllous leaves, with margin-

al petioles. Ovate symmetrical lamina at least 11.5 cm

long and 2.5 cm wide; base acute decurrent and apex

acute slightly convex. Margin entire, unlobed. First

vein category pinnate. Second vein category brochi-

dodromous; space between secondaries and their

angles of emergence slightly decreasing towards the

base. Third vein category random reticulate and sin-

uous, emerging at acute to perpendicular angles,

reaching the primary vein at right angles. Fourth

vein category (highest) regular polygonal reticulate.

Areoles well-developed, 4–5 sided. Ultimate marginal

venation looped.

bars=1 cm. (see page 35)

ntogenetic development with some irregular pattern in the shape of

advanced ontogenetic development of leaflets.

aflets showing the venation pattern.

e asymmetrical development of the apical leaflets.

. Scale bars=1 cm (except for Fig. 3=0.5 cm). (see page 36)

rn and the asymmetrical characteristic of leaflet bases.

ing a clear marginal vein and constricted and asymmetrical base.

the initial development of leaflets.

rn.

Plate I (Caption on page 34).

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–47 35

Plate II (Caption on page 34).

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–4736

Fig. 3. Line drawings of the venation pattern of all angiosperm morphotypes described. Scale bars=1 cm. A: Rogersia australis; based on

Holotype specimen MPEF-Pb-Mz 1133A. B: Morphotype 1; based on specimen MPEF-Pb-Mz 1142B. C: Morphotype 4; based on specimen

MPEF-Pb-Mz 1126A. D: Morphotype 3; based on specimen MPEF-Pb-Mz 1118. E: Thorphyllum patagonica; based on Holotype specimen

MPEF-Pb-Mz 1136A. F: Morphotype 2; based on specimen MPEF-Pb-Mz 1138. G: Kachaikenia compuesta: based on Holotype MPEF-Pb-Mz

1116.

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–47 37

Repository: Paleobotanical Collection, Museo Paleon-

tologico Egidio Feruglio MPEF-Pb.

Holotype: MPEF-Pb-Mz 1136.

Type locality: Arroyo Caballo Muerto Creek, San

Martin Lake area, western Santa Cruz province,

Argentina.

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–4738

Horizon: Uppermost part of the Kachaike Formation

at ACM Creek.

Studied material: MPEF Pb-Mz 1264, 1136 A-B,

1137, 1138, 1139, 1078.

Derivatio nominis: Thorphyllum honors Thor Halle

who was the pioneer in collecting and describing

fossil plants from the same area; patagonica refers

to the Patagonian region of southern Argentina.

Remarks: All the specimens we assigned to this taxon

are those whose venation system is clearly seen.

However, there are additional leaves whose general

shape and appearance are fairly similar to the ones

described here, but in these the venation pattern is not

preserved. Hence, it is possible that this morphospe-

cies is more abundant in the assemblage. The size of

the lamina is approximately 11.5 cm long and 2.5 cm

wide (L /W=4.6 :1) and only measurable in the type

specimen (Plate III, 1 and 2). A second specimen

preserves the apex (Plate III, 3), which is acute but

shows some degree of convexity in its angle. Areoles

are well-developed but veinlets have not been seen.

It is also interesting to note that the foliar mar-

gins, although entire, show some sort of imperfect

outline, suggesting certain primitiveness for this mor-

photype. This is also suggested from a probably

variable disposition in the widest part of the lamina,

which in one specimen (Plate III, 1) appears on the

lower half while in a second specimen (Plate III, 3),

although fragmentary, is probably displaced toward

the half lamina. In both cases, the venation pattern is

exactly the same.

Plate IV. Scale bars=1 cm. (see page 40)

1–5. Rogersia australis Cuneo et Gandolfo sp. nov. 1–2: Holotype

pattern. 3: Paratype (MPEF-Pb-Mz 1135A). Fragment of leaf sh

MPEF-Pb-Mz 1141A, B), detail of the venation pattern.

6. Morphotype 3 (MPEF-Pb-Mz 1118). Slightly fragmentary leaf

Plate III. Scale bars=1 cm. (see page 39)

1–3. Thorphyllum patagonica Cuneo et Gandolfo gen. et sp. nov. Hol

petiole, and venation pattern. 2: Leaf showing some insect dama

leaf showing the apex (MPEF-Pb-Mz 1264).

4. Morphotype 4 (MPEF-Pb-Mz 1126A). Rounded leaf showing t

5. Morphotype 2 (MPEF-Pb-Mz 1138). Fragmentary leaf with the

possible insect damage.

Two specimens (Plate III, 2 and 3) shows organic

degradation, probably associated with marginal insect

feeding. The presence of galls can also be detected on

the same leaf.

Comparisons: The venation pattern, shape and size of

Thorphyllum resemble those of Sapindopsis Fontaine

(1889). However, Sapindopsis is a genus erected for

compound leaves, and the leaves of Thorphyllum are

assumed to be simple. Moreover, the intercostals areas

of T. patagonica extend almost to the margins occu-

pying 90% of the hemi-lamina whilst in S. elliptica

they appear much shorter (60% or less).

Ficus fredericksburgensis Fontaine is another leaf

morphotype to some extent comparable with Sapin-

dopsis elliptica Fontaine (a fact already mentioned by

Fontaine, 1889) and also to T. patagonica (in partic-

ular because of it is simple). However, no meaningful

comparisons can be made among these species be-

cause details of higher venation orders in F. freder-

icksburgensis are unknown.

Myrtoidea patagonica (Passalıa et al., 2001), from

possible early Late Cretaceous sediments in southern

Patagonia, is an entire leaf approximately similar in

size to Thorphyllum patagonica, with well-devel-

oped intercostals areas. However, the presence of

well-developed intersecondary veins and an intramar-

ginal vein clearly separates it from T. patagonica.

Genus Rogersia Fontaine 1889

Rogersia australis Cuneo et Gandolfo sp. nov.

(Plate IV, Figs. 1, 2, 3; Fig. 3A.)

(MPEF-Pb-Mz 1133A, B). Leaf showing shape, apex and venation

owing the venation pattern and partial asymmetry of the blade. 4–5:

preserving general shape and venation pattern (unclear).

otype (MPEF-Pb-Mz 1136). 1: Leaf showing general shape, base and

ge. 3: A second specimen preserving the upper half of a fragmentary

he venation pattern.

upper half preserved showing the general venation pattern and some

Plate III (Caption on page 38).

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–47 39

Plate IV (Caption on page 38).

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–4740

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–47 41

Diagnosis: Simple microphyllous leaves, elliptic and

slightly symmetrical lamina. Base acute cuneate and

apex acute. Margin entire. First vein category pinnate,

weakly sinuous. Second vein category festooned bro-

chidodromous, highly decurrent with irregular spacing

and angles. Lacking intersecondary veins. Third vein

category alternate, sinuous, exmedially ramified,

emerging at acute or obtuse angles from the secondary

veins. Fourth category veins regular, polygonal retic-

ulate. Areoles well-developed, 3–4 sided. Ultimate

marginal venation looped.

Plate V. Morphotype 1.

1. MPEF-Pb-Mz 1142B. Fragmentary leaf showing shape, genera

2. MPEF-Pb-Mz 1142A. Detail of the venation pattern.

Repository: Paleobotanical Collection, Museo Paleon-

tologico Egidio Feruglio MPEF-Pb.

Holotype: MPEF-Pb-Mz 1133.

Paratype: MPEF-Pb-Mz 1135.

Type locality: Arroyo Caballo Muerto Creek, San

Martin Lake area, western Santa Cruz province,

Argentina.

Horizon: Uppermost part of the Kachaike Formation

at ACM Creek.

Studied material: MPEF-Pb-Mz 1133 A-B, 1134,

1135 A-B, 1141 A-B.

l venation pattern and petioled base.

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–4742

Derivatio nominis: Australis, from the southern

continents.

Remarks: This morphotype is represented by several

fragmentary specimens, the most complete up to 8 cm

long and 1.4 to 1.86 cm wide (L /W=5.7 :1); addi-

tionally, some of them preserve their apexes (Plate IV,

1) and part of their bases (Plate IV, 3). The margins

are always entire but irregular in terms of not showing

a perfect outline but some bexpansionsQ in the middle

of the lamina, which probably denotes a primitive

foliar type. Intercostal areas are almost parallel to

the midvein at the basal part of the leaf. The highest

venation order clearly observed is the fourth; howev-

er, it is quite possible that a fifth order is present as

well. In this regard, areoles formed by fourth order

veins do not show any preserved veinlets. In some

specimens, the main vein seems to divide the lamina

into asymmetrical halves (Plate IV, 3).

Comparisons: This morphotype shows some similar-

ities with Rogersia angustifolia Fontaine (1889) most-

ly in its general shape, size, base and apex shape, and

margins, and also in the type of secondary venation

(brochidodromous) in both species. An interesting

character of R. angustifolia is that the widest part of

the lamina is at or above the midpoint of its length

(Wolf et al., 1975), a feature that the Kachaike speci-

mens do not share, since in the latter the lamina is

widest at its midpoint. Another character shared with

the Patagonian material is that the blade and petiole

are poorly differentiated, as indicated by Doyle and

Hickey (1976). Consequently, we believe that our

material represents a different species of the same

genus, the main differences between the species

being the shape (elliptic as opposed to mostly obovate

in R. angustifolia), venation pattern (brochidodro-

mous but festooned in R. australis), and the L /W

ratio (higher in the new species).

Pons (1988, Fig. 16 b) illustrates a bfeuille insertae

sedisQ from late Albian sediments of Colombia. This

leaf shows a certain resemblance to our material,

particularly in the presence of an extended lamina

without a petiole as well as disorganized secondary

veins of brochidodromous type. Passalıa et al.

(2003) describe from the early Aptian Anfiteatro

Tico Fm. (lower Baquero Group) a fragmentary

bNymphaeaphyllQ morphotype whose venation sys-

tem shows a comparable festooned brochidodro-

mous pattern in the secondary and tertiary veins;

however, the midvein bifurcates and does not reach

the apex in this morphotype.

Morphotype 1

(Plate V, Figs. 1, 2; Fig. 3B.)

Description: This morphotype is characterized by sim-

ple microphyllous leaves, probably elliptic and slight-

ly asymmetric in shape; preserved length is 5.5 cm

and width up to 2.1 cm. It has an acute base and a

marginal petiole. The apex is not preserved (Plate V,

1). The margin is entire and unlobed. The first vein

category is pinnate and seems to be strong. The

secondary veins show a brochidodromous pattern;

these veins emerge at uniform angles and are irregu-

larly spaced, showing a slightly increased spacing

toward the base; intersecondary veins are absent or

loosely defined. The third vein category occurs in

regular polygons and is exmedially ramified, with

angles to primaries acute or irregular and inconsistent.

The fourth vein category is regular reticulate and

delimits polygonal, well-developed, 3–4 sided are-

oles. It is possible that the fifth category vein is

present and is dichotomous and the ultimate marginal

venation is looped.

Repository: Paleobotanical Collection, Museo Paleon-

tologico Egidio Feruglio MPEF-Pb.

Studied material: MPEF-Pb-Mz 1142 A-B.

Comparisons: This morphotype is represented by only

one fragmentary specimen (Plate V, 1 and 2). In

general, its venation pattern resembles that of Roger-

sia Fontaine. In this regard, its venation pattern could

be initially compared with that of R. australis, even

though the nature of insertion of the secondary veins

is more decurrent in R. australis. However, because it

has an acute base with a differentiated petiole, this

morphotype could not be included in the genus Roger-

sia. Indeed, this morphotype may more resemble

some forms of Ficophyllum Fontaine, such as the

specimens discussed and illustrated by Doyle and

Hickey (1976, Fig. 5) and Hickey and Doyle (1977,

Figs. 11 and 13). Mohr and Friis (2000) described

several angiosperm leaves from the Aptian–Albian

age Crato Formation in Brazil. Their Type 6 leaf,

although smaller than ours and with noticeable inter-

secondary veins, shows a very similar type of vena-

tion pattern (pinnate brochidodromous with irregular

higher venation orders).

Since this morphotype is represented by only one

partially preserved specimen, it is necessary to have

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–47 43

additional material before evaluating its affinities and

placing it taxonomically.

Morphotype 2

(Plate III, Fig. 5; Fig. 3F.)

Description: This morphotype is characterized by a

simple, microphyllous leaf with a symmetric, proba-

bly elliptic to obovate lamina, 3 cm in length and 2.3

cm in width (L /W=1.3 :1). The apex is acute convex,

base unknown. The margin is entire, and unlobed. The

first vein category is pinnate while the second vein

category is eucamptodromous with well spaced veins

and weak intersecondary veins. The third vein cate-

gory is in regular polygons and the tertiary veins have

straight courses; angles to primary vein are mostly

perpendicular and increasing basally. The fourth vein

category is regular polygonal reticulate and delimits

well-developed 3–4 sided areoles with no veinlets.

The ultimate marginal venation is looped.

Repository: Paleobotanical Collection, Museo Paleon-

tologico Egidio Feruglio MPEF-Pb.

Studied material: MPEF Pb-Mz 1138.

Comparisons: This morphotype resembles Ficophyl-

lum crassinerve Fontaine, as seen in the line drawing

of one specimen shown in Plate 144, 3 (Fontaine,

1889, page 291). This is a fragment of an apical

portion of a leaf showing a venation pattern with

pronounced arches reaching the margin similar to

the ones observed in the Patagonian specimen. None-

theless, F. crassinerve shows more closely spaced

secondary veins, more obtuse emergence angle and

better-defined intercostal areas. The specimen could

probably be referred with doubts as F. crassinerve

Fontaine. However, until more specimens are found,

we prefer to designate it as a morphotype.

Morphotype 3

(Plate IV, Fig. 6; Fig. 3D.)

Description: The leaf is simple, notophyllous, and the

lamina is elliptic symmetrical; 2.8 cm in length and

1.1 cm in width (L /W=2.7 :1). The base is acute

decurrent, and the apex is acute. The margin is entire

and unlobed. The first vein category is pinnate. The

second vein category is weakly brochidodromous

with irregularly spaced veins; they emerge at acute

angles that decrease towards the base. The interse-

condary veins are lacking. Higher vein orders not

visible (not preserved), although the ultimate marginal

venation seems to be looped.

Repository: Paleobotanical Collection, Museo Paleon-

tologico Egidio Feruglio MPEF-Pb.

Studied material: MPEF Pb-Mz 1118.

Comparisons: This specimen can be compared with

Ficophyllum tenuinerve Fontaine, especially in its

size, shape, a decurrent base, and venation pattern,

with secondary brochidodromous arches in more

than one row between the midrib and the margins.

Dicotilophyllum sp. B (Samilyna, 1960), described

from the Lower Cretaceous of the Kolyma basin

in Russia, shows intercostal areas rather similar to

morphotype 3.

Morphotype 4

(Plate III, Fig. 4; Fig. 3C.)

Description: The leaf assigned to this morphotype is

simple, and microphyllous, with an asymmetrical and

rounded lamina, 3 cm long and 3.5 cm wide (L /

W=0.86 :1). The base is wide obtuse and slightly

cordate and lacks petiole. The margin is entire and

unlobed. The first vein category is pinnate and the

second vein category is eucamptodromous, with 3

basal veins and simple agrophic veins. The secondary

veins are spaced regularly, becoming more crowded

towards the base; they emerge at acute angles that

become more obtuse towards base. The intersecond-

ary veins are weak. The third vein category is prob-

ably random reticulate with possibly straight course

and inconsistent angle of emergence. Highest vein

categories are not preserved.

Repository: Paleobotanical Collection, Museo Paleon-

tologico Egidio Feruglio MPEF-Pb.

Studied material: MPEF Pb-Mz 1126 A-B.

Remarks: Morphological features in this morpho-

type (in particular its shape and venation pattern)

look, to some extent, relatively confuse and uncer-

tain, and it is possible that some kind of abnormal

development could have affected the leaf resulting

in a sort of bsickQ leaf blade. Since only one

specimen has been recovered, possibilities remain

open on this respect and others related with true

affinities of this morphotype.

Comparisons: Among the leaf morphotypes known in

the bmidQ Cretaceous, our specimen partly resembles

the genus Proteaephyllum Fontaine (1889). P. reni-

forme Fontaine, in particular, has a similar outline and

size, but the venation pattern is different, our speci-

men showing a strong midvein and arched secondary

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–4744

vein course. This last character, however, is seen in

other species of the genus, such as P. ovatum Fon-

taine, but that species differs in shape. Therefore, the

Kachaike specimen combines features from two dif-

ferent species of the genus. In this regard, Fontaine

(1889) indicated more than a century ago that the

genus could be divided into two subgenera: one of

them (rotundatum) including orbicular/reniform

leaves with no midvein and the other (elongatum)

including elongate leaves with a marked midvein.

On this basis, our specimen could probably represent

a transitional or intermediate form that shows char-

acteristics of both possible subgenera, probably repre-

senting a new genus, although more material is

required to confirm this interpretation.

Walkom (1919) described Phyllites sp. from the

Lower Cretaceous of Australia as a circular leaf with

an entire margin. From his reconstruction on page 17,

Fig. 3, the venation pattern resembles, to some extent,

the one present in morphotype 4. However, the poor

preservation of the Australian specimen precludes a

more detailed comparison.

Teixeira (1948) described a Lower Cretaceous leaf

characterized by its rounded outline. Nonetheless, the

presence of a crenate margin as well as a clearly

different venation pattern separates it from morpho-

type 4.

5. Discussion

The leaf morphotypes described here generally

show a pinnate–brochidodromous or eucamptodro-

mous venation pattern, with relatively irregular in-

tercostal areas and disorganized higher venation

categories. These angiosperm leaf morphotypes are

microphylls or nothophylls, with entire and unlobed

margins. These features characterize the morpho-

types as lower rank leaves (1r) in the sense of

Hickey (1971), which are hardly comparable with

modern angiosperm families. This major feature is

shared with other early late Cretaceous angiosperm-

bearing floras, such as those from Brazil (Mohr and

Friis, 2000), the United States (Hickey and Doyle,

1977), and China (Sun and Dilcher, 2002), suggest-

ing a comparable worldwide morphological pattern

in most of the angiosperm components of the Cre-

taceous vegetation. In particular, the northern Gond-

wana flora from the Crato formation in Brazil

(Mohr and Friis, 2000; Mohr and Rydin, 2002;

Mohr and Eklund, 2003; Mohr and de Oliveira,

2004) shows a clear different spectrum in terms of

the angiosperm component. This is related not only

to a different biogeographic context but also to a

paleoclimatic setting with a strong dry season result-

ing in special morphological adaptations of the

flowering plants and a proliferation of Ephedraceae

that clearly supports this interpretation. Instead, the

Kachaike flora, even though in its early study stage,

does not show special autoecological adaptations at

the time that certain diversity and abundance of

ferns suggest that humid conditions in the environ-

ment prevailed.

The composition of the Kachaike flora indicates

that angiosperms were still subordinate elements by

the early Albian in southern South America, a fact

also corroborated by the pollen record. In compari-

son with the older Baquero flora (Romero and Arch-

angelsky, 1986; Passalıa and Cladera, 2003; Passalıa

et al., 2003) of the same region, the angiosperm

component of the Kachaike megaflora shows the

following differences: (1) higher number of leaf

morphotypes; (2) no common angiosperm leaf mor-

photypes; (3) a larger angiosperm component in

relation with the non-angiosperm components of

the flora; and (4) a higher number of angiosperms

forms in the pollen record.

The initial results from slightly younger floras

(Passalıa, 2003; Iglesias et al., 2004), show that they

do not share any of the leaf morphotypes recognized

in the Kachaike flora. Moreover, the angiosperm flora

from Bajo de los Corrales in Patagonia (Albian or

younger?) has been characterized as a rank II flora

with more defined morphological traits – including

leaves with toothed margins not seen in Kachaike –

that allow to link these angiosperm morphotypes to

magnoliids (Passalıa et al., 2003). Thus, it appears

possible that a certain bevolutionaryQ pattern in terms

of morphology could be present in southern Argentina

during the late early and early late Cretaceous. This

pattern, if confirmed, might be useful for biostratigra-

phical purposes in continental sequences.

In particular, the information provided by the

Kachaike angiosperm assemblage does not define

aspects concerning the age per se. However, it must

be emphasized that the degree of foliar evolution and

R. Cuneo, M.A. Gandolfo / Review of Palaeobotany and Palynology 136 (2005) 29–47 45

venation patterns described in this assemblage shows

similarities with those described from the Zone I of

the Potomac Group (Hickey and Doyle, 1977; Doyle

and Hickey, 1976), the age of which has been consid-

ered as late Aptian–early Albian. Even though only

one morphotype has been found in common between

the Zone 1 flora of the Potomac Group and the

Kachaike flora (i.e. Rogersia Fontaine), there seem

to be others that share some morphological traits in

terms of venation patterns, size, shape, etc. This could

suggest that the evolution of early angiosperms in

both hemispheres was probably not so different, at

least in relation to some morphological traits.

Leaf morphotypes of Sapindophyll, Platanophyll

or even Cinnamomophyll type (in the sense of Crab-

tree, 1987) that characterize the middle Albian to

early Cenomanian floras of the Rocky Mountains

are not recorded at the Kachaike flora. However,

they can be found in the angiosperm component of

the younger Mata Amarilla Fm. in southern Patago-

nia (Iglesias et al., 2004). Moreover, lower rank

leaves (such as Rogersia Fontaine) are not recog-

nized in floras of this age in North or South Amer-

ica. The late Hauterivian/early Barremian flora of

Jixi (Sun and Dilcher, 2002) shows very few strictly

comparable morphotypes even though it can be con-

sidered as primitive as the Kachaike flora. In this

regard the Jixi flora shows an equivalent develop-

ment in terms of its morphological bevolutionaryQdegree (i.e. leaves mostly showing a pinnate–brochi-

dodromous venation pattern), even though this flora

is older than any other South or North American

early–middle Cretaceous floras.

The late Albian angiospermoid flora described

from Antarctica by Cantrill and Nichols (1996)

does not show any particular leaf traits resembling

the Kachaike flora. For instance, the actinodromous,

acrodromous and craspedodromous venation patterns

that seem to dominate the Antarctic morphotypes are

not seen in the Kachaike flora. The Albian flora of

Antarctica is the oldest record of angiosperm macro-

floral (Cantrill and Poole, 2002) whereas the micro-

floral record is as old as early Albian (Dettman and

Thomson, 1987). Both seem to be younger than the

first Patagonian floras where angiosperms were pres-

ent, which date from the early Aptian or even earlier.

This is probably related to the southward radiation of

this plant group, which was able to reach southern-

most latitudes only when climatic conditions were

appropriate, assuming a tropical origin for early

angiosperms. Cantrill (2000) suggested that the Ant-

arctic Peninsula might have acted as a gateway

between South America and Australia, filtering

plant migration. This mechanism, associated with a

paleoclimatic gradient (Cantrill, 2000) could have

been in some way responsible for differentiating

angiospermoids between South America and Antarc-

tica. However, if migration routes toward Antarctica

had operated through South America, some of the

morphotypes present in the Antarctic should have

been present in Patagonia before the Early Aptian,

which is not the case as suggested from the Baquero

and Kachaike floras. Therefore, alternative migration

routes could have been acting at least at the initial

migration phase. Later in the Cretaceous when

warmer and more homogenous climatic conditions

prevailed in southern latitudes, it is possible that a

stronger floral exchange might have taken place in

Gondwana. This theory will only be tested when a

more detailed knowledge of the angiosperms in the

late Cretaceous is achieved.

Acknowledgments

Thanks are due to David Cantrill and Elizabeth

Hermsen for their critical suggestions on an early

manuscript. Comments from three anonymous

reviewers also contributed to improve the manuscript.

M. A. Gandolfo expresses her gratitude to the Amer-

ican Philosophical Society for funding.

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