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RE: Mojoceratops and venomous Sinornithosaurus



  Re: *Mojoceratops*: Ah, another taxon to add to my "probable synonyms turned 
into nomina dubia" list, although a funky name. And just so that it's clear, 
no, I've not read the paper; my comment above is intended to remark on the fact 
that a series of taxa have been erected only seeming after previous potential 
synonyms are rendered "nomen dubium" status, permitting not only a full genus, 
but a full species, status for a new specimen. It stresses the purpose of 
implying referral of a specimen which is name-bearing to a newly erected taxon 
with its own name-bearing type.

  In context to longitudinal dental root-crown sulci (I've not read Gianechini 
et al,, but based only on the comments on the list), though:

  While previously it has been suggested that the longitudinal sulcus on the 
labial surface of theropod teeth are a taphonomic artefact, it should be noted 
that some taxa possess a specific "bilobate" form of the root where the root 
and the basal part of the crown appear to have a rounded-hourglass (or 
bilobate) aspect in cross-section. This is not a typical preservational 
artefact, as it occurs in skulls and dentition with otherwise no other signs of 
distortion, and include specimens preserved outside of the typical bedding 
"crushing"plane. While it may still be taphonomic than actual, at least some 
taxa with extreme thin teeth (< 25% labiolingually wider than mesiodistally 
long) including *Allosaurus* and some dromaeosaurids and troodonts (not all of 
them) have this feature and it is seemingly omnipresent regardless of mode of 
preservation.

  However, a preservational artefact does exist in which the sulcus is 
abnormally present, and this occurs when there is a distinct angular, and 
hairline, fracture associated with bending through gradual, persistent 
compression. These fractures will often have an irregular line when viewed in 
detail, but otherwise appear as though the sulcus is V-shaped. Extremes of this 
type of compression/bending (I am unsure of the process) may include split 
teeth, where a crown is longitudnally split in two, a mesial and a distal side.

  You will find similar fractures in long bones compressed along their axis, 
deforming them from their normal shape.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
> Date: Wed, 7 Jul 2010 22:32:24 +0300
> From: villesink@gmail.com
> To: dinosaur@usc.edu
> Subject: Mojoceratops and venomous Sinornithosaurus
>
> Nicholas R. Longrich. 2010 Mojoceratops perifania, A New Chasmosaurine
> Ceratopsid from the Late Campanian of Western Canada. Journal of
> Paleontology 84(4):681-694.
>
>
> Abstract
>
> A new genus of long-horned chasmosaurine ceratopsid is described from
> the Dinosaur Park Formation (upper Campanian) of Western Canada.
> Mojoceratops perifania is represented by a skull and a parietal from
> the Dinosaur Park Formation of Alberta and an isolated parietal from
> the Dinosaur Park Formation of Saskatchewan. Several other specimens
> are provisionally referred to this taxon. While Mojoceratops shares
> many plesiomorphies with Chasmosaurus, the animal lacks the
> forward-curving parietal epoccipitals and reduced postorbital horns
> that diagnose the genus Chasmosaurus, and it differs from all other
> chasmosaurines in exhibiting a prominent sulcus on the anterior margin
> of the parietal, swellings on the anterodorsal surface of the parietal
> rami, and a small accessory process on the first parietal epoccipital.
> Other unusual features include anteriorly extended parietal fenestrae,
> a broad, heart-shaped frill, and transverse expansion of the
> postfrontal fontanelle. The type material of “Eoceratops canadensis”
> and “Chasmosaurus kaiseni” are nondiagnostic and these names are
> therefore considered nomina dubia, but their morphology is consistent
> with Mojoceratops and they probably belong to this genus. The frill of
> Mojoceratops shows marked variation. Some of this variation probably
> results from intraspecific variation or ontogenetic changes, but
> because the Dinosaur Park Formation encompasses more than a million
> years of time, evolution may explain some of these differences.
> Phylogenetic analysis shows that Mojoceratops forms a clade with
> Agujaceratops mariscalensis; Chasmosaurus is the most basal member of
> Chasmosaurinae.
>
>
> (I thought we heard last of this venomous Sinornithosaurus , but I
> guess not....)
>
> Federico A. Gianechini, Federico L. Agnolín and Martín D. Ezcurra 2010
> A reassessment of the purported venom delivery system of the bird-like
> raptor Sinornithosaurus
> Paläontologische Zeitschrift, online first
>
> Abstract
> Gong and colleagues recently described unusual traits in the
> dromaeosaurid Sinornithosaurus that were interpreted as the first
> evidence of a venomous dinosaur. This interpretation was based on
> extremely elongated maxillary teeth, morphologically similar to those
> present in poisonous snakes; labial grooves on maxillary and dentary
> tooth crowns; and an additional ornamented depression in the lateral
> surface of the maxillary bone (subfenestral fossa). A reappraisal of
> each of these morphological traits is provided here in light of
> comparisons with other theropod dinosaurs and previous discussions for
> inferring poisonous capabilities in fossil taxa. We fail to recognize
> unambiguous evidence supporting the presence of a venom delivery
> system in Sinornithosaurus. For example, the extremely elongated teeth
> seem to be a taphonomic artifact due to the displacement of teeth
> outside the alveoli; the labial grooves are present in a wide variety
> of theropods; and no strong evidence for the lodging of a venomous
> gland is recognized. In contrast, the cranial and dental anatomy of
> Sinornithosaurus is congruent with that of other dromaeosaurids. The
> weak support for a venomous Sinornithosaurus renders unlikely the
> ecological model proposed by Gong and colleagues for this predatory
> dinosaur.
>
> and a response
>
> Enpu Gong,Larry D. Martin, David A. Burnham and Amanda R. Falk 2010
> Evidence for a venomous Sinornithosaurus
> Paläontologische Zeitschrift, online first
>
> Also a new species of atoposaurid crocodylian
>
> Komsorn Lauprasert, Chalida Laojumpon, Wanitchaphat Saenphala, Gilles
> Cuny,Kumthorn Thirakhupt and Varavudh Suteethorn 2010
> Atoposaurid crocodyliforms from the Khorat Group of Thailand: first
> record of Theriosuchus from Southeast Asia
> Paläontologische Zeitschrift, online first
>
> Abstract
> We describe a partial crocodilian skull from the Mesozoic non-marine
> sediments of the Khorat Plateau Sao Khua Formation
> (Berriasian-Barremian) in northeastern Thailand and assign it to
> Theriosuchus grandinaris sp. nov. An isolated dentary from the Phu
> Kradung Formation (latest Jurassic–Early Cretaceous) is also
> tentatively assigned to the genus Theriosuchus, and an isolated tooth
> from the Khok Kruat Formation (Aptian-Albian) may belong to this
> genus. The Thai fossils represent the first unambiguous evidence of
> presence of Theriosuchus outside Europe. Its occurrence in Thailand
> increases the known diversity of neosuchian crocodyliforms from
> Southeast Asia and suggests that Atoposauridae had a wide geographical
> distribution from the Late Jurassic to the Early Cretaceous.
>
> btw if someone has access to those last three papers I would gladly
> recieve a copy.
>
>
> Cheers
>
> -Ville
                                          
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