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Early Dinosaur Evolution Symposium Volume
Hi All -
This is now officially out as _Historical Biology_ 19(1) -- some of
these were mentioned earlier, but some weren't, and some that were initially
listed aren't in the volume (but are still in the journal's "on-line early"
Bonaparte, J.F., Brea, G., Schultz, C.L., and Martinelli, A.G. 2006. A new
specimen of Guaibasaurus candelariensis (basal Saurischia) from the Late
Triassic Caturrita Formation of southern Brazil. Historical Biology
19(1):73-82. doi: 10.1080/08912960600866862.
ABSTRACT: The comparison of the anatomy of a second incomplete skeleton of
Guaibasaurus candelariensis to that of basal Saurischia suggests that the
origin of the "Prosauropoda" was from unknown basal saurischians, after
separating from theropods (except herrerasaurids). Guaibasaurus and
Saturnalia are part of this early dichotomy, and they bear mixed
characters-states of basal theropods and "prosauropods" type. The Late
Triassic age of both Guaibasaurus and Saturnalia (the latter is older)
predates the 'dominance' of basal sauropodomorphs as well as the appearance
of the basal theropod Zupaysaurus, both recorded from the upper Los
Colorados Formation of Argentina.
Ezcurra, M.D., and Novas, F.E. 2006. Phylogenetic relationships of the
Triassic theropod Zupaysaurus rougieri from NW Argentina. Historical Biology
19(1):35-72. doi: 10.1080/08912960600845791.
ABSTRACT: The anatomy and phylogenetic relationships of the Upper Triassic
theropod Zupaysaurus rougieri are reviewed. This taxon is represented by a
nearly complete skull and fragmentary postcranial remains recovered from the
Los Colorados Formation (Norian), NW Argentina. Originally, Zupaysaurus
rougieri was considered a basal member of the Tetanurae, but its anatomy
closely resembles that of the Coelophysoidea, supporting its nesting within
this theropodan subclade. Thus reinterpreted, Zupaysaurus represents the
first record of coelophysoids in South America. Phylogenetic analyses
perfomed in this study depict Zupaysaurus as a non-coelophysid coelophysoid.
Autopomorphic traits of Zupaysaurus include: maxillary-jugal ventral margin
forming an obtuse angle in lateral view, tibia with a very deep and caudally
open caudal fossa for the reception of an astragalar caudal process. Within
the phylogenetic context outlined here, the derived features shared with
Tetanurae (e.g. maxillary fenestra, caudally forked ascending ramus of the
maxilla) are better interpreted as homoplasies rather than tetanuran derived
Ferigolo, J., and Langer, M.C. 2006. A Late Triassic dinosauriform from
south Brazil and the origin of the ornithischian predentary bone. Historical
Biology 19(1):23-33. doi: 10.1080/08912960600845767.
ABSTRACT: The South American Late Triassic offers the most comprehensive
window to the early radiation of dinosaurs. This is enhanced by the
discovery of Sacisaurus agudoensis, a new dinosauriform from the Caturrita
Formation of Brazil. Various morphological features suggest its close
phylogenetic affinity to Silesaurus, and both may be basal ornithischian
dinosaurs. Sacisaurus has a pair of elements forming the tip of its lower
jaw, hypothesized to be equivalent to the ornithischian predentary. This
suggests that during an initial stage of their evolution, those dinosaurs
had a paired predentary, which later fused into a single structure. As an
originally paired bone, the predentary is comparable to elements that more
often form the vertebrate mandible, such as the mentomeckelian bone.
Although synapomorphic for ornithischians, the predentary does not seem
neomorphic for the group, but primarily homologous to parts of the
symphyseal region of the lower jaw of other vertebrates.
Irmis, R.B., Parker, W.G., Nesbitt, S.J., and Liu, J. 2006. Early
ornithischian dinosaurs: the Triassic record. Historical Biology 19(1):3-22.
ABSTRACT: Ornithischian dinosaurs are one of the most taxonomically diverse
dinosaur clades during the Mesozoic, yet their origin and early
diversification remain virtually unknown. In recent years, several new
Triassic ornithischian taxa have been proposed, mostly based upon isolated
teeth. New discoveries of skeletal material of some of these tooth taxa
indicate that these teeth can no longer be assigned to the Ornithischia
using unambiguous synapomorphies. The Triassic record of ornithischian
dinosaurs now comprises only three probable occurrences: Pisanosaurus and an
unnamed heterodontosaurid from Argentina, and an unnamed specimen from the
uppermost Triassic of South Africa. This revised Triassic record suggests
that ornithischians were not very diverse or abundant through the Triassic,
and there are large gaps in the Triassic ornithischian fossil record.
Moreover, traditional living analogues for interpreting the feeding ecology
of early ornithischians from their tooth morphology are generally
inappropriate, and "herbivorous" archosaur teeth such as those found in
early ornithischians are not necessarily diagnostic of herbivorous feeding.
Marsicano, C.A., Domnanovich, N.S., and Mancuso, A.C. 2006. Dinosaur
origins: evidence from the footprint record. Historical Biology 19(1):83-91.
ABSTRACT: Triassic tracks and trackways assigned to dinosaur trackmakers or
closest relatives have been mentioned from several Middle to the latest
Triassic successions from both northern and southern Pangea. At present, the
earliest gondwanan records are those from the Middle Triassic Los Rastros
Formation in west-central Argentina. A reanalysis of Los Rastros ichnites at
the Ischichuca area, including new material, has revealed the presence of a
more diverse ichnofauna than previously suspected. The ichnocoenosis
includes several tracks and trackways of bipeds with functionally tridactyl
digitigrade pes, well developed claws, and a parasagittal posture of the
hindlimbs. Previously, some large tridactyl footprints from the Ischichuca
area were allied to theropod dinosaurs, although no synapomophies are
preserved in the three-toed footprints that might discriminate among
theropods, basal saurischians and basal ornithischian groups as their
possible trackmakers. If the Ischichuca trackmakers are referred to a
dinosaur taxon and/or to a close dinosaur sister-taxon, their presence in
the Los Rastros levels suggests that derived dinosauriforms (including
dinosaurs) had diverged and acquired their characteristic functionally
tridactyl pes by at least the Middle Triassic, something that the
body-fossil record has failed to document to date.
Pol, D., and Powell, J.E. 2006. Skull anatomy of Mussaurus patagonicus
(Dinosauria: Sauropodomorpha) from the Late Triassic of Patagonia.
Historical Biology 19(1):125-144. doi: 10.1080/08912960601140085.
ABSTRACT: The skull anatomy of Mussaurus patagonicus from the Upper Triassic
Laguna Colorada Formation is described based on a revision of the type
material and several recently found specimens. The studied material include
two distinct size classes of individuals. The type material consists of
extremely young individuals whereas the new specimens are interpreted as
juvenile or subadult individuals. The latter are significantly larger,
having a skull approximately three times longer than the type material. The
skull anatomy of this taxon shows derived characters shared with some basal
sauropodomorphs and eusauropods, which are absent in other basal
sauropodomorphs (e.g. Thecodontosaurus, Plateosaurus). These include the
presence of an extension of the infratemporal fenestra ventral to the orbit,
dorsal and anterior rami of quadratojugal subperpendicular to each other,
dorsoventral expansion of dentary at mandibular symphysis, slightly
procumbent teeth with broad serrations restricted to the apical region
(absent in some teeth). Differences among the studied specimens helps to
understand the early ontogenetic changes occurring in this basal
sauropodomorph, revealing major changes in the rostral and temporal regions.
Sereno, P.C. 2006. The phylogenetic relationships of early dinosaurs: a
comparative report. Historical Biology 19(1):145-155. doi:
ABSTRACT: Surprising new anatomical information has come to light for the
early dinosaurs Eoraptor lunensis and Herrerasaurus ischigualastensis.
Eoraptor has a mid mandibular jaw joint, and Herrerasaurus has a
promaxillary fenestra at the anterior end of the antorbital fossa. Initial
cladistic interpretation placed Herrerasaurus outside Dinosauria. Since
then, Eoraptor and Herrerasaurus have been placed at the base of Saurischia
or within Theropoda in two large-scale quantitative analyses. A comparative
approach is taken here to show, first, that character choice is a major
factor behind differing results; only half of the character data critical
for each interpretation is incorporated into the opposing analysis. In that
shared portion of data, furthermore, nearly 40 percent of character state
scores vary for identical, or comparable, ingroup taxa. Resolving these
conflictive interpretations is clearly where future progress will be made in
understanding early dinosaur phylogenesis.
Yates, A.M. 2006. Solving a dinosaurian puzzle: the identity of Aliwalia rex
Galton. Historical Biology 19(1):92-123. doi: 10.1080/08912960600866953.
ABSTRACT: Eucnemesaurus fortis Van Hoepen 1920 from the Late Triassic of
South Africa is demonstrated to be the senior synonym of the puzzling
dinosaur taxon Aliwalia rex Galton 1985. A new specimen of this poorly-known
taxon is described. Eucnemesaurus is clearly a sauropodomorph and increases
the diversity of sauropodomorph taxa in the South African Late Triassic to
six. It shares a number of femoral synapomorphies with Riojasaurus from the
Late Triassic of Argentina and Riojasauridae tax. nov. is erected to
accommodate them. These conclusions are supported by a comprehensive
cladistic analysis of 46 sauropodomorph and other basal dinosauriform taxa
using 353 osteological characters. This analysis also supports the
paraphyletic nature of the traditional 'prosauropod' assemblage.
Jerry D. Harris
Director of Paleontology
Dixie State College
225 South 700 East
St. George, UT 84770 USA
Phone: (435) 652-7758
Fax: (435) 656-4022
"Trying to estimate the divergence times
of fungal, algal or prokaryotic groups on
the basis of a partial reptilian fossil and
protein sequences from mice and humans
is like trying to decipher Demotic Egyptian with
the help of an odometer and the Oxford
-- D. Graur & W. Martin (_Trends
in Genetics_ 20, 2004)