37Fossil News – Fall 2017
Would You Recognize A Holotype If It Hit You in the Chevron?ere’s a trick question: What’s thedifference between the “type
specimen” and the “holotype “of aspecies? The question is tricky be-cause the two terms refer to exactlythe same thing.
In understanding what paleon-tologists and other scientists meanwhen they use these words, the defi-nition from the Oxford English Dic-tionary is a good place to start: “Aspecimen chosen as the basis of thefirst description of a new spe-cies.” The OED dates the first useof the word to an article by thefamous invertebrate paleontolo-gist, Charles Schuchert (1858-1942), director of the PeabodyMuseum of Natural History at YaleUniversity from 1904-1923, the firstpresident of the Paleontological So-ciety, and an avid fossil-hound whoamassed one of the largest brachio-pod collections in the world.
In April 1897, Schuchert wrote inScience: “A holotype in natural his-tory is a particular individual delib-erately selected by the author of aspecies, or it may be the only ex-
ample of a species known at the timeof original publication.” In otherwords, a holotype or type specimenis the physical specimen upon whicha taxon (generally but not always agenus or species) is established—or,in the jargon, “erected.”
Holotypes are meant to beregistered and deposited with amuseum or institution where, atleast in theory, they can be consultedby others. Institutions are typically
identified by a code (YPB is the YalePeabody Museum, FMNH is the FieldMuseum, and BHI is the Black HillsInstitute—as in BHI 3033, theTyrannosaurus illustrated by FabioPastori in this issue).1
This institution code is followedby numbers or letters that identifythe specific specimen in theinstitution’s collections, allowing theholotype—again theoretically—to
be available as a basis of comparisonand standard of reference for anyfuture finds. Is this specimen I’vefound of the same species? Checkthe description of the holotype and,if possible, the actual specimen itself.
And how about another term, aslong as we’re throwing them out:paratype. Paratypes are specimensidentical to the holotype and includedin the “type series” by the author inthe original publication of the new
taxon. (Botany has somewhatdifferent rules for the use of theterm “paratype,” however.) So, ifa paleontologist collected fivespecimens of the same speciesof a brand-new brachiopod she
wanted to name, and mentionedthem all as part of the series of speci-mens examined, one would becomethe holotype and the other fourwould be paratypes.
So far so good. Unfortunately, itturns out that things are a little morecomplicated than that.
Currently, a mini-debate haserupted over whether holotype mustalways mean the original specimen
Chevrons are a series of bones on the underside of the tail of many reptiles (as well as some mammals).Pictured is a replica of an eleven-inch specimen of a Diplodocus chevron.
RECENT ISSUESIN PALEONTOLOGY
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38 Fossil News – Fall 2017
upon which a taxon is erected, or whether the definitionshould be “loosened” to encompass the specimen thatbest represents or is most diagnostic of the species.
The problem for paleontology—and especially for ver-tebrate and dinosaurian paleontology—becomes almostinstantly obvious. In the case of specimens that tend to bedescribed as whole entities—an echinoid, an insect (fossilor not), an extant bird—the holotype is virtually always theentire organism or,at least, its complete fossilized remains.But when a new dinosaurian species is established on thebasis of a few scattered vertebrae or a tooth, what hap-penswhen later workersdiscovera femur or apartial skull?How can they compare the holotype to these discoveriesand come to any useful conclusions?
The doubt that arises spontaneously, of course, is this:Doesn’t this suggest that a certain number of describeddinosaurs species may be invalid? In other words,couldn’t partial remains sometimes be assigned to sepa-rate species even when they might, in fact, have comefrom the same kind of organism? And the spontaneous
answer to both questions is: Yes.At the heart of the current con-
troversy is a 2016 petition byTschopp and Mateus that
asked the In-ternational Com-mission on ZoologicalNomenclature (ICZN) to desig-nate a different specimen ofDiplodocus carnegii, a Jurassic mem-ber of the group of giant dinosaursknown as Diplodocids, named forthe distinctive “double-beamed”chevron bones on the ventralsurface of their tails, as the holotypeof the species.
University of Bristol (UK) paleontologist Michael P.Taylor, who curates the Sauropod Vertebra Picture of theWeek Blog (svpow.com), not only supports the petition,he goes even further, saying that the “ICZN was neverdesigned with dinosaurs in mind in the first place”(Taylor, 2016a). The problem with the current Diplodocusholotype, as Taylor explained in his formal statement tothe ICZN in support of the change,
is a familiar one to dinosaurian workers: whenworking with very large animals that died manymillions of years ago, most specimens are incom-plete, and often very uninformative.... [This]issuewas greatly exacerbated by the “Bone Wars” of E.D. Cope and O. C. Marsh, rival palaeontologists inthe late 19th century of the USA, who each aimedto outdo the other by naming more species of fos-
sil animals. As a result, many dinosaurian spe-cies were named on the basis of non-diagnosticremains.... Despite being one of the most com-pletely known of all dinosaurs, and among thosebest known to the general public, Diplodocus suf-fers badly from this syndrome. It was founded byMarsh on a non-diagnostic fragmentary speci-men (YPM 1920), which supposedly functions asthe type specimen of the type species, D. longus.
The petition’s authors themselves argued that“Diplodocus should not be typified by an undiagnosabletype species,” and that “the undiagnosable state of theholotype of D. longus (YPM 1920, a partial tail and achevron)” is good reason to replace it with “the muchbetter represented [CM 84 specimen of ] D. carnegiiHatcher, 1901. CM 84, they go on to say, is a “well-pre-served and mostly articulated specimen,” casts of which“are on display in various museums around the world.”
Citizen scientist Mickey Mortimer, however, curatorof the Theropod Database Blog (theropoddatabase.blogspot.com), opposes the petition, arguing thatthe ICZN code in no way requires the holotype tobe diagnostic, meaning that it need not be thebest-preserved or best-described
specimen. As a technical matter, thatstatement is true enough:
The ICZN code doesn’trequire it. But should it?
Holotypes aresome-times lost,
destroyed in fires or natural disasters, or never de-posited in the first place and, in those cases, thererarely appears to be much argument over replacingthem with what are termed “neotypes.” In the case
of Diplodocus and the 2016 petition, however, there aredeeper questions of whether dinosaurs “deserve spe-cial treatment,” as Taylor has written, precisely becausethey are “in many cases ... represented by eroded anddistorted fossils of a tiny part of the animal [and arethus] already an aberration from the perspective of theICZN” (Taylor, 2016b).
As of this writing, nearly 120 cases remain open be-fore the ICZN, from arachnids to brachiopods, lemurs tosponges, but Diplodocus isn’t among them. In fact, Case3700 is entirely missing from its database. Perhaps thefundamental question raised by the Tschopp and Mateuspetition—what exact function a holotype is meant toserve—is giving the committee pause.
—Wendell Ricketts
39Fossil News – Fall 2017
[Facing page: Illustration of Diplodocus carnegii byDmitry Bogdanov ([email protected]); used via a Cre-ative Commons CC BY 3.0 license.]
References
Taylor, Michael P. (2016a). Comment on the Pro-posed Designation of Diplodocus carnegii Hatcher, 1901As the Type Species of Diplodocus Marsh, 1878. (Case3700; see BZN 73: 17-24). <https://svpow.files.wordpress.com/2016/09/taylor2016-support-for-diplodocus-carnegii.pdf>
Taylor, Michael P. (2016b, 13 September). What Isthe Nature and Purpose of a Type Specimen? SauropodVertebra Picture of the Week. <https://svpow.com/2016/09/13/what-is-the-nature-and-purpose-of-a-type-specimen>
Tschopp, E. & Mateus, O. (2016). Case 3700.Diplodocus Marsh, 1878 (Dinosauria, Sauropoda): Pro-posed Designation of D. carnegii Hatcher, 1901 as theType Species. Bulletin of Zoological Nomenclature 73(1):17–24. <http://www.bioone.org/doi/10.21805/bzn.v73i1.a22>
Note1 Anyone geeking out over the curation of natural-his-tory collections should consult the database of morethan 7,000 institutions and their codes maintained byGRBio, the Global Registry of Biodiversity Repositories:http://grbio.org/find-biorepositories.
