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Chirotherium tracks from Spain + Mongolian Cretaceous turtle fossils + Urodele genome



Ben Creisler
bcreisler@gmail.com


A number of recent non-dino papers:


Ignacio Díaz-Martínez, Diego Castanera, José Manuel J.M. Gasca & José
Ignacio Canudo (2015)
A reappraisal of the Middle Triassic chirotheriid Chirotherium
ibericus Navás, 1906 (Iberian Range NE Spain), with comments on the
Triassic tetrapod track biochronology of the Iberian Peninsula.
PeerJ PrePrints 3:e1155
doi: https://dx.doi.org/10.7287/peerj.preprints.933v1
https://peerj.com/preprints/933/


Triassic vertebrate tracks are known from the beginning of the 19th
century and have a worldwide distribution. Several Triassic track
ichnoassemblages and ichnotaxa have a restricted stratigraphic range
and are useful in biochronology and biostratigraphy. The record of
Triassic tracks in the Iberian Peninsula has gone almost unnoticed
although more than 25 localities have been described since 1897. In
one of these localities, the naturalist Longinos Navás described the
ichnotaxon Chirotherium ibericus in 1906.The vertebrate tracks are in
two sandy slabs from the Anisian (Middle Triassic) of the Moncayo
massif (Zaragoza, Spain). In a recent revision, new, previously
undescribed vertebrate tracks have been identified. The tracks
considered to be C. ibericus as well as other tracks with the same
morphology from both slabs have been classified as Chirotherium
barthii. The rest of the tracks have been assigned to Chirotheriidae
indet., Rhynchosauroides isp. and undetermined material. This new
identification of C. barthii at the Navás site adds new data to the
Iberian record of this ichnotaxon, which is characterized by the small
size of the tracks when compared with the main occurrences of this
ichnotaxon elsewhere. As at the Navás tracksite, the Anisian C.
barthii-Rhynchosauroides ichnoassemblage has been found in other
coeval localities in Iberia and worldwide. This ichnoassemblage
belongs to the upper Olenekian-lower Anisian interval according to
previous biochronological proposals. Analysis of the Triassic Iberian
record of tetrapod tracks is uneven in terms of abundance over time.
>From the earliest Triassic to the latest Lower Triassic the record is
very scarce, with Rhynchosauroides being the only known ichnotaxon.
Rhynchosauroides covers a wide temporal range and gives poor
information for biochronology. The record from the uppermost Lower
Triassic to the Middle Triassic is abundant. The highest
ichnodiversity has been reported for the Anisian with an assemblage
composed of Dicynodontipus, Procolophonichnium, Rhynchosauroides,
Rotodactylus, Chirotherium, Isochirotherium, Coelurosaurichnus and
Paratrisauropus. The Iberian track record from the Anisian is coherent
with the global biochronology proposed for Triassic tetrapod tracks.
Nevertheless, the scarcity of track occurrences during the late
Olenekian and Ladinian prevents analysis of the corresponding
biochrons. Finally, although the Iberian record for the Upper Triassic
is not abundant, the presence of Eubrontes, Anchisauripus and probably
Brachychirotherium is coherent with the global track biochronology as
well. Thus, the Triassic track record in the Iberian Peninsula matches
the expected record for this age on the basis of a global
biochronological approach, supporting the idea that vertebrate
Triassic tracks are a useful tool in biochronology.


===

Donald B. Brinkman, Hai-Yan Tong, Hong Li, Yan Sun, Jian-Sheng Zhang,
Pascal Godefroit & Zhe-Min Zhang (2015)
New exceptionally well-preserved specimens of “Zangerlia”
neimongolensis from Bayan Mandahu, Inner Mongolia, and their taxonomic
significance.
Comptes Rendus Palevol (advance online publication)
http://www.sciencedirect.com/science/article/pii/S1631068315000081


Two exceptionally well-preserved specimens of “Zangerlia”
neimongolensis provide additional information on the structure of the
skull, shell and limbs of this taxon. These specimens show that the
carapace is more similar to that of Hanbogdemys than was previously
recognized. A PAUP analysis results in a single most parsimonious
cladogram in which the type species of Zangerlia, Zangerlia
testudinimorpha is separated from other species that have been
included in that genus while “Z.” neimongolensis, “Zangerlia”
ukaachelys and “Zangerlia” dzamynchondi and Jiangxichelys are grouped
together. Both specimens are exceptional in being preserved in a
life-like position: one is preserved with the skull in a retracted
position; the other with the head and left forelimb both protracted
and in a raised position. These positions suggest that they were
entombed while still alive. Thus these specimens provide additional
examples of rapid burial of vertebrates in the Bayan Mandahu locality,
most likely from either by sand storms that dumped massive amounts of
sand over a short period of time or by collapse of individuals in
burrows.

====


Michel Laurin, Aurore Canoville, Mikayla Struble, Chris Organ & Vivian
de Buffrénil (2015)
Early genome size increase in urodeles.
Comptes Rendus Palevol (advance online publication)
http://www.sciencedirect.com/science/article/pii/S1631068315000111

Urodeles have the largest genomes among extant tetrapods, varying
greatly between metamorphic and neotenic species, which have the
smallest and the largest genomes of the group, respectively. The
evolutionary tempo and mode of genome size expansion in urodeles are
poorly documented, especially because genome size does not directly
fossilize. Consequently, the ancestral state for genome size, and
therefore, the polarity of its evolution in urodeles are uncertain.
However, recent studies have demonstrated that osteocyte (lacuna) size
is correlated with genome size. Below, we present histological data,
on osteocyte lacuna size from one of the oldest known stem-urodeles,
Marmorerpeton, from the Middle Jurassic (Bathonian, 166–168 Ma), as
well as on five extant urodele species. Our analysis of these taxa,
coupled with previously published data, suggests that stem-urodeles
had already evolved large genomes, typical of extant urodeles by the
Bathonian.