NEW PERMO-TRIASSIC TRACK PAPERS

[darren.naish@port.ac.uk]

New issue of _Palaeontology_ arrived this morning. 
Includes...

Braddy, S. J., Morrisey, L. B. & Yates, A. M. 2003. 
Amphibian swimming traces from the Lower Permian of 
southern New Mexico. _Palaeontology_ 46, 671-683.

Some nice tracks from the Robledo Mountains ichnofauna 
were produced by swimming tetrapods: though noted in 
print before they'd been regarded as invertebrates traces 
(which explains why Simon Braddy, best known for his 
work on eurypterids, is involved). One set of tracks (a 
sinusoidal, continuous body trace with paired manus and 
pes prints) appears to have been produced by an 80-90 mm 
long aquatic tetrapod with a salamander-like body shape. 
The contendors considered are temnospondyls, microsaurs, 
nectrideans or archeriids. Given the large adult sizes of 
some of the members of these groups, the trackmaker may 
have been a juvenile.

Rather more surprising is the new ichnotaxon 
_Serpentichnus robledoensis_, a trace which recalls that 
produced by side-winding snakes (i.e., in being 
discontinuous and consisting of subparallel long body 
traces) yet preserves pes impressions. Don't forget these 
tracks were formed subaqueously. The trackmaker must 
have been a long-bodied tetrapod (two trackways of this 
taxon are reported, they represent animals with body lengths 
of 160 and 240 mm respectively) with reduced limbs: the 
only contendors are the lysorophians (aistopods are all 
limbless and long-bodied microsaurs are not big enough or 
long-bodied enough), with the Lower Permian 
_Brachydectes_ being the most likely trackmaker. So, at 
least some lysorophians were aquatic side-winders.. (!!), 
how incredibly cool.

Rainforth, E. C. 2003. Revision and re-evaluation of the 
Early Jurassic dinosaurian ichnogneus _Otozoum_. 
_Palaeontology_ 46, 803-838.

A taxonomic revision and detailed discussion is given of 
_Otozoum_. Suggested over the years to have been 
produced by an ornithopod (Lull, Thulborn), plateosaur 
(Nopsca) or basal thyreophoran (Gierlinski, Wright), 
Rainforth shows that prosauropods (s. l.) best fit the 
predicted trackmaker morphology: s. l. because 
_Anchisaurus_ is suggested as the best trackmaker for N. 
American _O. moodii_, while _Anchisaurus_, 
_Ammosaurus_ and _Massospondylys_ are regarded as 
good candidates for _O. pollex_ from Lesotho.

 _Kalosauropus_ Ellenberger is sunk into _Otozoum_ and 
Triassic tracks previously referred to _Otozoum_ are 
actually the crurotarsan track _Pseudotetrasauropus_. There 
is an interesting discussion of whether pad distribution 
matches pedal osteology: while earlier authors (Hitchcock, 
Lull, Heilmann etc) concluded that dinosaurs were either all 
mesarthral (= pads underlying middle of phalanges) or all 
arthral (= pads underlying interphalangeal joints), recent 
work on birds (Rainforth cites Smith and Farlow, in press) 
shows that, even within a species, there are arthal and 
mesarthral individuals, and dinosaurs seem to have been 
pretty variable. Presumably the arthral condition is primitive 
for dinosaurs but various lineages may have evolved the 
mesarthral condition.

Other purported prosauropod trackways are reviewed and 
characters observed in tracks are interpreted in a 
phylogenetic framework. Surprisingly, prosauropod (s. l.) 
tracks are absent from Late Triassic strata as Rainforth 
shows that reports of such are erroneous.

There's more to it - anyone into tracks will get a lot out of 
this paper.

-- 
Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth UK, PO1 3QL

email: darren.naish@port.ac.uk
tel: 023 92846045