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Adventures in Etymology: Oplosaurus, Mastodonsaurus



From: Ben Creisler bh480@scn.org
Adventures in Etymology: Oplosaurus, Mastodonsaurus

I recently had a chance to do some research at the 
University of California library at Berkeley, and have 
come back a bit humbled--a couple of old etymologies I 
thought I had resolved in fact are much WEIRDER than I 
could have guessed. I was consulted on both of  these 
etymologies for books or museum diplays, and worked with 
the best info I had a hand--the Greek and Latin roots were 
seemingly fine, but the REASON and meaning I proposed for 
each name now appear to be off.  The original publications 
in each case are found in special or stored collections 
that need to be consulted in person (no requests for 
photocopies allowed!). The Berkeley palaeo library stuff 
has been in major flux for a few years and somewhat 
difficult to track down--the contents of the Earth 
Sciences Library were transferred in part to the 
Biosciences Library, the Main Library, special collections 
and into storage when Paleontology became part of  
Department of Integrative Biology rather than Earth 
Sciences. Here are a few examples with quotations from the 
original texts to spare others the trouble of tracking 
them down:

Oplosaurus armatus a mosasaur!?
List-member Darren Naish asked me about this puzzler for 
his excellent  book Dinosaurs of the Isle of Wight, and I 
provided my "educated" (now maybe debunked!) guess based 
on what I could find at the University of Washington 
Library. The name almost certainly comes from Greek hoplon 
meaning "weapon, shield, arms, armor" (dropping the 
initial Greek "h" is this case in not uncommon in 
scientific names)--but why Gervais proposed  such a name 
for what is now known to be a sauropod tooth is a mystery 
that turns out to be even weirder than Darren or I 
suspected.  The only material I had at hand before 
checking sources at Berkeley was the original description 
of the tooth and illustration of the tooth in an 1852  
British journal, in which Mantell commented that the tooth 
might come from an animal like Hylaeosaurus armatus. It 
seemed plausible to me at the time that Gervais might have 
assumed the tooth came from an armored animal similar to 
Hylaeosaurus, which would explain his choice of the name 
Oplosaurus armatus (note the same species name 
meaning "armed"). WRONG! I checked on some of Gervais' 
works available at Berkeley and it turns out he thought 
the tooth he called Oplosaurus came from a MOSASAURID-
related reptile, not a dinosaur! He  rejected Owen's 
Dinosauria and used  the Mosasauridae as a kind of catch-
all group to embrace a wide range of reptiles distinct 
from the Megalosauridae and the Iguanodontidae (in which 
he included Hylaeosaurus). Did Gervais think the tooth 
came from a meat-eating animal, in which case Oplosaurus 
might mean "weapon lizard" or maybe "armed lizard"  for 
its teeth? Frankly, the thick spoon-shaped tooth does not 
look particularly "weapon-like" to me. The species 
name "armatus" is Latin for "armed"--again, the tooth 
doesn't seem like a weapon to be armed with! Maybe he 
originally came up with the name based on Mantell's 
comments about the armored Hylaeosaurus, retained the name 
but then later changed his classification of the animal 
before he went into print.  Here's the description from 
the second edition of his Zoologie et Paléontologie 
françaises (1856), page 464.

OPLOSAURUS

"On peut en effet regarder comme indiquant un genre à part 
de Mosasauridés, une dent singulière que M. Wright a 
recueillie dans l'argile wéaldienne de Brighton-Bay, à 
L'île de Wight, et dont il donné la figure et une courte 
description dans les Annals and Mag. of nat. hist., pour 
le mois d'août 1852. Cette dent, qu'il a bien voulu nous 
montrer pour avoir notre avis sur l'animal dont elle 
provient, est longue de 0,090, couronne et racine. Sa 
partie coronale, plus large que la radiculaire, est 
convexe d'un côté, subconvexe de l'autre; ses bords 
antérieurs et posterieurs sont en carène, et il y a 
l'indication d'une troisième carène verticale sur le 
milieu de la face convexe; la racine est en partie 
enveloppé de matière osseuse, montrant que son mode 
d'implantation était le même que dan les Mosasaures et 
Léiodons. On pourra donner à  l'espèce type du genre 
Oplosaurus le nom d'armatus."

[translated (over)literally:
"One can in effect regard as indicating a genus distinct 
from the Mosasauridae a singular tooth that Mr. Wright 
collected in the Wealden clay at Brighton Bay, Isle of 
Wight, and for which he provided a figure and a short 
description in the Annals and Magazine of Natural History 
for the month of August 1852. This tooth, which he greatly 
wished to show us to have our opinion on the animal to 
which it belonged, is [85mm] long, crown and root. Its 
crown, larger  than the root, is convex on one side, 
subconvex on the other; the front and back edges are 
keeled, and there is an indication of a third vertical 
keel on the  middle of the convex face; the root is partly 
covered in bony material, showing that its mode of 
implantation was the same as in Mosasaurus and Leiodon. 
One may give the type species for the genus Oplosaurus the 
name 'armatus'."
****************

Mastodonsaurus "teat-like tooth lizard" (NOT "Mastodon 
(size) lizard")
When the American Museum updated their displays, they 
asked me about the meaning of Mastodonsaurus,  a giant (20 
ft) Triassic amphibian, and I suggested "Mastodon (size) 
lizard" based on the confidently stated explanation given 
by Charles Gilmore in 1944 in the Smithsonian Series vol. 
8 (Fishes, Amphibians, Reptiles) (pg. 166): "In the year 
1824 Professor Jaeger discovered in Wuerttemberg, Germany, 
the fossil remains of an amphibian so large that he 
applied to it the name Mastodonsaurus, not because it had 
any relationship to the elephantlike mastodon--which is, 
of course, a mammal--but in reference to its very great 
size."
I found the same seemingly plausible etymology indicated 
in some dictionaries (Mastodon + saurus), and had the 
meaning further confirmed by a well-known  and long 
established vertebrate paleontologist with an interest in 
nomenclature. Other sources gave a confusing array of less 
obvious alternate meanings--in addition to the 
literal "breast tooth lizard" (Greek mastos "breast, 
nipple, dug"+ Greek odon "tooth") in some books, Agassiz 
gave the derivation as "jaw tooth lizard" and Rainer  
Schoch in his excellent recent monograph explained it 
as "wart-toothed lizard." A few old German sources gave 
the meaning as "zitze" tooth lizard, which can 
mean "nipple" or "teat." Comparisons with a "breast" 
or "nipple" did not make much sense to me based on the 
long conical type tooth with a damaged tip.   Owen, of 
course, tried to change the name to Labyrinthodon because 
he thought Mastodonsaurus was misleading for unavoidably 
associating the tooth either with a Mastodon or with a 
breast, and implying identification as a reptile rather 
than an amphibian! There is no substitute for the original 
description, however, and I was finally able to read 
Jaeger's first description of the single holotype tooth in 
the rare books collection at Berkeley. Note that the name 
Mastodonsaurus was first proposed for a single very large 
striated tusk-like tooth (still the largest amphibian 
tooth known) without any associated bones--and Jaeger was 
also the "perceptive" researcher who came up with the name 
Phytosaurus "plant lizard" for a meat-eating archosaur! 
Here's what Jaeger says in part in "Jaeger, G F. 1828. 
Uber die fossile reptilien, welche in Wurtemberg 
aufgefunden worden sind.  Stuttgart, J.B. Metzler 48"  
(pages 35-36):
MASTODONSAURUS
"Dieser Zahn is naemlich besonders ausgezeichnet durch 
seine zitzenartige Spitze...der Zahn endigt sicht in eine 
gewoelbte Spitze, die aber in ihrer Mitte eine 
nabelfoerimige Vertiefung, und in der Mitte derselben 
wieder eine kleine Erhoehung hat." 
Which translates loosely as:
"This tooth is most particularly remarkable for its teat-
like tip...the tooth terminates in a domed tip, which has 
in turn a navel-shaped depression in its center, and 
furthermore a small knob in the center itself." 

Maybe it did not occur to the good doctor Jaeger that the 
tip was actually damaged, worn or broken, creating the 
shape that apparently reminded him in some way of a 
mammalian teat!

Jaeger later correctly associated the tooth with some 
large bones from the back of a skull, which he had named 
Salamandroides giganteus "gigantic salamandar-like one" 
for their resemblance to bones of living salamanders.  
Since the name Mastodonsaurus had priority by a couple of 
pages in the original book, the official name became 
Mastodonsaurus giganteus.

I guess I should contact the American Museum and ask them 
to change their display. Kind of embarrassing...