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Albertonectes, elasmosaur with 76 neck vertebrae



From: Ben Creisler
bcreisler@gmail.com

Another paper in the new JVP. Interesting details: Albertonectes has
76 cervicals, the highest cervical count known among vertebrates. Its
neck is 7 m long. With its missing skull added, it likely would have
been about 11.5 m in total length.

Tai Kubo, Mark T. Mitchell & Donald M. Henderson (2012)
Albertonectes vanderveldei, a new elasmosaur (Reptilia, Sauropterygia)
from the Upper Cretaceous of Alberta.
Journal of Vertebrate Paleontology 32(3): 557-572
DOI:10.1080/02724634.2012.658124
http://www.tandfonline.com/doi/abs/10.1080/02724634.2012.658124


ABSTRACT
A new elasmosaurid plesiosaur, Albertonectes vanderveldei, gen. et sp.
nov., is described on the basis of an almost complete postcranial
skeleton from the upper Campanian, Bearpaw Formation in Alberta,
Canada. The new taxon is distinguished by a unique set of
characters—76 cervicals, lateral longitudinal ridge on posterior-most
cervicals, relatively wide clavicular arch, tapered ventral projection
at the median symphysis of coracoids, pointed anterolateral projection
of pubis, fused posterior-most caudal vertebrae, and a relatively
slender humerus. Ninety-seven chert gastroliths were also recovered
with the specimen, and their mean diameters range from <1 to 13.5 cm.
Shape analysis indicates that most of the gastroliths were ingested in
the vicinity of a beach environment. Evidence that the carcass was
scavenged by sharks includes a tooth-marked coracoid, two shed
Squalicorax sp. teeth, and small, localized disruptions to the
skeleton. Preliminary phylogenetic analysis confirms the inclusion of
Albertonectes in a clade comprised of ‘middle’ to Late Cretaceous,
long-necked elasmosaurid plesiosaurs. The number of cervical vertebrae
associated with different elasmosaur genera does not show any
correlation with phylogeny. Both neck and total body length of
Albertonectes are the longest among known elasmosaurs, and highlight
the morphological extremes attained by this group of plesiosaurs.


====

Another new marine reptile paper:


Marianella Talevi, Marta Fernández & Leonardo Salgado (2012)
ONTOGENETIC VARIATION IN THE BONE HISTOLOGY OF CAYPULLISAURUS
BONAPARTEI FERNÁNDEZ, 1997 (ICHTHYOSAURIA: OPHTHALMOSAURIDAE).
Ameghiniana 49(1): 38-46
http://www.ameghiniana.org.ar/index.php/ameghiniana/article/view/403

In order to explore the osteohistological ontogenetic variation in
ichthyosaurs, we studied the bone microstructure of the ophtalmosaurid
Caypullisaurus bonapartei Fernandez. The analyzed thin sections were
obtained from three ribs belonging to different individuals
(MLP85-I-15-1, 83-XI-15-1 and 83-XI-16-1), from the Vaca Muerta
Formation (Tithonian, Late Jurassic), in the Neuquén Basin
(Argentina). The ontogenetic stages of these specimens have previously
been determined based on the morphology of the humerus and the
sclerotic rings. The first specimen is composed entirely of finely
spongy tissue distributed around the medullary cavity.
Microscopically, the spongy bone is secondary, with abundant inner
spaces delimited by bone trabeculae. There are numerous overlapping
generations of lamellar bone. The second specimen (a juvenile) shows
primary spongy bone surrounding the medullary cavity and Sharpey’s
fibers. The third specimen lacks a medullary cavity; instead, the
medullary region is occupied by secondary spongy bone, uniformly
distributed through the entire section. These results suggest that the
macroscopic changes classically attributable to ontogeny have a
correlation in bone microstructure. The bones of immature individuals
show some primary bone, while the bones of the mature specimens are
characterized by the exclusive presence of secondary bone. These
features are easily identifiable, and provide an auxiliary criterion
for the determination of ontogenetic stages in incomplete and
fragmentary specimens.