Paul's Mass Estimates -- Outtakes

[Jaime Headden <qi_leong@hotmail.com>]

In Greg Paul's recent supplement to dinosaur mass estimates 
(http://gspauldino.com/data.html), a few notes:

1. Therizinosaurs are separated from a section titled Theropods and Birds (and 
after "Prosauropods"), in a simile to _The Dinosauria_ (Weishampel et al., eds, 
first edition), but also to Paul's argument in 1984 (JVP 4) that therizinosaurs 
were not theropods. I wonder if this is considered phylogenetic in any way, as 
the other sections are consistent to their grades at least.

2. *Abelisaurus garrodi*. I was unaware of this species, as I understand there 
is only *A. comahuensis* referred to the monotypic *Abelisaurus*. There is an 
*Aucasaurus garridoi*, so I wonder if this is a typo ... but of which taxon? 
The specimen used (MCF-PVPH-236) is the type of *Aucasaurus garridoi*.

3. Some estimates of mass are derived from obvious juveniles, but Paul 
considers some specimens to be embryos. *Scansoriopteryx* is listed as one such 
specimen (based on the Czerckas and Yuan, 2002 paper, the IVPP specimen 
referred to *Epidendrosaurus* is not listed), but the slightly larger 
*Epidexipteryx* is simply listed without any label on the apparent age of the 
specimen (Zhang et al., _Nature_ 455 consider it to be a subadult), despite use 
of the lebel "juvenile" for *Juravenator* and *Scipionyx* (of which the latter 
is argued to be a hathcling and therefore the closest to an actual embryo among 
specimens Paul uses here).

4. *Chirostenotes* is estimated from a composite. It should be noted that the 
only published femur derives from TMP 79.20.1, which is crushed obliquely to 
the craniocaudal axis, and flattened in a way that certainly distorts both its 
circumference and length (especially as the proximal end is deflected 
proximally so that the femoral head is certainly deformed); this makes 
reconstruction difficult. The types of *C. pergracilis,* *Macrophalangia 
canadensis* and *Caenagnathus* presumably derive from similarly sized animals, 
but TMP 79.20.1 is from an animal ~2-3% larger based on the dimensions of the 
relatively undistorted manual and pedal material, and the largest specimen 
referred to *C. pergracilis*, ROM 43250, was over 15% larger than the holotype 
and may not belong to *C. pergracilis* due to variation in the ischium, sacrum, 
and its geologically younger age.

5. *Stenonychosaurus* is used over *Troodon,* which is fine (the latter is just 
based on teeth, the former on a head-less skeleton, and there are at least two 
or more tooth morphotypes which have yet to be discriminated specifically from 
the various Campanian/Maastricthian formations in which they occur). However, 
the specimen composition provided includes a relatviely complete skeleton 
referred to *Stenonychosaurus inequalis* (MOR specimens), as well as the 
holotypes for *Saurornithoides mongoliensis* (AMNH 6516) and *Zanabazar junior* 
(GI 100/1). While these fascinating animals may all be synonymous with one 
another, Paul's previous penchant for lumping results in *Hypacrosaurus 
casuarius*, fails to lump *Maiasaurua* + *Brachylophosaurus*, splits the 
various European iguanodonts, segregates *Brontosaurus* from *Apatosaurus*, 
etc., so this seems to be some fairly specific splitting/lumping. Moreover, 
Norell et al. (_AM Novitates_) distinguishes *Zanabazar* and supports splitting 
various troodontids on the basis several cranial and postcranial features, and 
supports further the distinction of various Mongolian troodontids (although 
lumps the North American ones).

Cheers,

  Jaime A. Headden

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