[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Trachodon?

In a message dated 95-08-21 15:18:11 EDT, us009472@interramp.com (Michael
Edward Purvis) writes:

>  Requesting clarification... remarks I've read in different
>reference materials lead me to believe that the genus 
>"Trachodon" has been labeled invalid at some point between 
>the present time & when I first saw the name back during my 
>grade school years.
> Anyone care to fill me in?:)

Well--I can post English-language excerpts from parts 1 and 2 of my review of
Ornithopoda for Japan's _Dino-Frontline_. I hope you find them helpful.
(Unfortunately, italics and boldface can't be sent through the list. Hope
this is all still readable. Sorry about the repetitiveness of some parts;
these excerpts are from two articles published 3 months apart, so a certain
amount is unavoidable.)

>From Part 1:

        In the mid-to-late 1850s, ornithopod discoveries began to occur in North
America, the fruits of enthusiastic fossil-collecting in the newly acquired
territories of the western United States. In 1855, Ferdinand Vandiveer
Hayden, whom readers of my reviews have already met as the "man who picks up
stones running," shipped an assemblage of fossil-vertebrate fragments,
primarily teeth, to paleontologist Joseph Leidy at the Academy of Natural
Sciences of Philadelphia. Among these were an unworn, lozenge-shaped tooth
crown and some 17 other more or less worn but otherwise similar crowns from
the Judith River Formation of what was then Nebraska Territory. In March
1856, Leidy erected the new genus and species Trachodon mirabilis (from the
Greek trachys, "rough," and odon, "tooth"; and the Latin mirabilis,
"wonderful" or "strange") for two of the teeth; the one with the unworn crown
he considered the "most important." Much later, that specimen (ANSP 9260) was
formally declared the lectotype specimen by Richard Swann Lull and Nelda E.
Wright in their fabulous 1942 monograph, Hadrosaurian Dinosaurs of North
America (Geological Society of America Special Paper #40). The second tooth,
incidentally, turned out to belong to an indeterminate ceratopian, not to an
ornithopod: the world's first ceratopian specimen to be scientifically
described (as I noted in my prior review of Ceratopia). Of the remaining 16
fragmentary teeth, most are duckbilled ornithopod and a few are ceratopian.
They, too, reside in the Academy of Natural Sciences collection, as
paralectotypes under the same specimen number as the lectotype.
        From Hayden Leidy also received two caudal vertebrae (USNM 219 and 221) 
a toe bone (specifically, a proximal medial pedal phalanx, USNM 220; Figure
10) out of the Lance Formation (then known as the Great Lignite Formation)
near Grand River, South Dakota (then also part of Nebraska Territory). Later
in 1856, Leidy made them syntypes of a "deino-saurian as colossal as the
Iguanodon of England," Thespesius occidentalis (from the Greek thespesios,
meaning "wonderfully mighty and immense"; and the Latin occidentalis, meaning
"western"). In 1860, Leidy reported a third large caudal vertebra of what
seemed to be the same species, presented to the Academy of Natural Sciences
by US Army Captain Alfred Sully. Sully had received it from a local Indian
and passed it along. It apparently came from the same whereabouts as the
syntypes; most likely it still lies in the Academy's collection, though I
have not yet been able to ascertain its specimen number.
        In those days, such bits and pieces were distinctive enough to warrant
creating new genera and species, but we now know several different genera of
duckbilled dinosaurs from both Judith River and Lance time with teeth and
skeletal elements similar to those described by Leidy, and there is no way to
decide which of them (if any) is Trachodon or Thespesius. So each of Leidy's
genera is presently considered doubtful--a nomen dubium. At best, we can
tentatively identify Trachodon as a Judith River lambeosaurid, or crested
duckbilled dinosaur, and Thespesius as a Lance hadrosaurid, or flat-headed
duckbilled dinosaur. Being doubtful genera, Trachodon and Thespesius are no
longer used as the generic names of new species.
        As Charles Mortram Sternberg pointed out in 1936, the size and angle of 
tooth crown of Trachodon strongly suggest its lambeosaurid nature, but in
many dinosaur books the name Trachodon came unfortunately to be attached to a
much better-known genus of flat-headed duckbill (usually Hadrosaurus,
Edmontosaurus [=Anatosaurus], or Anatotitan: Hadrosaurus was even synonymized
with Trachodon at one time). Perhaps this was because the flat-headed,
strongly duckbilled skull of Anatotitan copei was initially referred to
Trachodon mirabilis by Edward Drinker Cope in 1883 (though under the name
Diclonius mirabilis; more about this situation in part 2). This is how
dinosaur aficionados of the 1950s (such as I) envisaged it. Several duckbill
species, hadrosaurid and lambeosaurid, were first erected within Trachodon
and Thespesius, and many more were at one time or another referred to those
genera, but most have since found more congenial homes in better-defined

>From Part 2:

Cope's Duckbilled Dinosaur
        Fragmentary remains of large ornithopods continued to accumulate with 
new dinosaur-hunting expedition out west, but they were for the most part
heartbreakingly incomplete. But in 1882, Jacob Lawson Wortman and R. S. Hill,
two well-known fossil collectors working for Cope in the Lance Formation near
the Moreau River north of the Black Hills of South Dakota, unearthed the
first nearly complete hadrosaurid skeleton, including a magnificent skull,
ever discovered (Figure 48). Just as the Bernissart beasts corrected many
misconceptions about the anatomy of Iguanodon, so did the new Lance
hadrosaurid add to the knowledge gathered by Joseph Leidy from the New Jersey
Hadrosaurus some 25 years earlier.
        The next year (1883), Cope named this dinosaur Diclonius mirabilis, a 
combination of generic and trivial names he created by referring Leidy's
species Trachodon mirabilis to his own 1876 tooth genus Diclonius. He saw
that some of the teeth closely matched the type tooth of Trachodon mirabilis
and, thinking that Leidy had abandoned the genus Trachodon, he substituted
Diclonius for it. Note that the skeleton is not the type specimen of
Diclonius mirabilis; the type specimen is still the Trachodon mirabilis tooth
Leidy described. This was the fourth species in the genus Diclonius, which by
then absolutely nobody except Cope was using. Cope's paper described and
illustrated mainly the skull, the first good hadrosaurid skull to be
described and the first one to clearly show the flattened "duckbill" for
which these dinosaurs became famous.
        Diclonius was dismissed as a synonym of Trachodon (or Hadrosaurus) by
practically all other paleontologists, especially Marsh. So, in one fell
swoop, Cope had given his dinosaur three names instead of just one: Diclonius
mirabilis, Trachodon mirabilis, and Hadrosaurus mirabilis, depending on whose
synonymy was used. This situation is the origin of the otherwise
unsubstantiated idea that the dinosaurs Trachodon and Hadrosaurus had wide,
flattened duckbills, and for countless illustrations of duckbilled dinosaurs
labeled Trachodon and Hadrosaurus in popular dinosaur books all the way into
the 1960s.
        In 1899, shortly after Cope's death, Henry Fairfield Osborn enjoined the
American Museum of Natural History in New York to purchase the Cope
collection, and the "Diclonius" skeleton was one of the prizes therein. As
plans were being formulated to mount the skeleton in 1904, word came of a
second skeleton discovered at Crooked Creek, Montana (also Lance Formation).
A rancher named Oscar Hunter had been riding across the badlands with a
companion when they came across the large skeleton weathering out of a hill.
To settle an argument about whether it was stone or buffalo bone, Hunter
kicked the tops off all the exposed vertebrae and rib heads, proving they
were stone. Soon another rancher, Alfred "Doc" Sensiba, heard of the find
and, in a bit of frontier negotiating, traded a revolver ("six-shooter") to
Hunter for the rights to the skeleton. In 1906, Sensiba and his brother sold
their rights to Barnum Brown and his workmen, who excavated it for the
American Museum. Hunter is said to have later traded the six-shooter for a
pinto pony he named "Dinosaur."
        In 1908, the two skeletons were mounted together, side by side, at the
American Museum. The one from the Cope collection (AMNH 5730) was given a
quadrupedal pose, as if foraging; the one from the Sensiba brothers (AMNH
5886) was mounted erect, as if rearing up for a look around. They were left
unnamed and were identified only as "trachodont" dinosaurs, although Brown
called them both Trachodon in his April 1908 report on their exhibition in
the American Museum Journal. It was not until 1942 that they were chosen as
holotype (the quadrupedal specimen) and plesiotype (the bipedal specimen) of
the species Anatosaurus copei by Lull and Nelda E. Wright, in their
unsurpassed monograph Hadrosaurian Dinosaurs of North America (Geological
Society of America Special Papers #40: xi + 242 pp. + 31 plates). Anatosaurus
copei thus became the fourth name given to Cope's duckbilled dinosaur.
        To get ahead of the story a bit, the problem of a proper name for Cope's
hadrosaur did not end even with Lull & Wright. Work on hadrosaurids in the
1970s, when a great number of specimens had become available, showed that the
distinctions drawn by Lull & Wright between Anatosaurus and the earlier-named
hadrosaurid Edmontosaurus were based on specific rather than on generic
separation. More precisely, the type species of Anatosaurus (Anatosaurus
annectens) was shown to belong to the earlier-named genus Edmontosaurus, but
as a species (Edmontosaurus annectens) different from the type species of
Edmontosaurus (Edmontosaurus regalis). Michael Keith Brett-Surman, who
carried out much of this work for his Master's and doctoral dissertations,
also realized that Cope's hadrosaurid, unlike the other species of
Anatosaurus, was too distinctive to belong in the genus Edmontosaurus; it
required a new generic name. But in the meantime, before Brett-Surman
published the description of the new genus, it came to be called
Edmontosaurus copei--the fifth name to be applied to Cope's duckbilled
        Brett-Surman's description of the new genus, with type species 
copei ("Cope's duck-giant"), appeared in an appendix to an article on
hadrosaurid skull morphometrics by Ralph E. Chapman and Brett-Surman, in the
book Dinosaur Systematics (Cambridge University Press, 1990). It is the sixth
and, almost certainly, last name to be applied to that species. Donald Baird,
then at Princeton University, suggested the generic name Anatotitan to
Brett-Surman. So, when the American Museum of Natural History reopened its
extensively remodeled dinosaur galleries to the public in 1995, Brown's
"trachodont" dinosaurs were finally labeled with their correct name.

George O.