[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

JVP 25(3)

New in the _Journal of Vertebrate Paleontology_, 25 (3) this month, we have a
series of papers on dinosaurian ossified "tendons" and their morphological
analogues, and growth structure in hadrosaurs. We also have a paper on the date
of the Daohugou site from which the fauna originates, but it is anecdotal. And
finally, a new specimen of *Neuquensaurus* shows that the two species are
probably the same species showing sexual variation through robusticity and a
unique ossification of the sacrum.

  First, dinosaurs:

  Organ, C. L. and J. Adams. 2005. The histology of ossified tendon in
    dinosaurs. _Journal of Vertebrate Paleontology_ 25(3):602-613.

  "Intratendinous ossification is widespread in dinosaurs (including birds).
   Although intratendinous ossification in living birds is well understood, the
   physiological process of tendon metaplasia and associated histological
   variability in Dinosauria are not. Therefore, ossified tendons were
   histologically sampled acrsss extinct dinosaurian clades. Tendons of living
   birds and alligators were also sampled. Despite various anatomical locations
   and large differences in body size, ossified tendons were found to possess
   uniform microstructure even in specimens that do not normally experience
   intratendinous ossification (such as *Spinostropheus* and *Camarasaurus*).
   The ossified tendons of non-avian dinosaurs are largely indistinguishable
   from skeletal bone with respect to microanatomical features. However,
   ossified tendons in birds lack periosteal bone and associated fibrolamellar
   structures associated with ornithischian dinosaur tendons. Variation in
   periosteal bone occurs along the length of individual tendons. Ossified
   tendons from marginocephalians are unique in that they have large quantities
   of anisotropic fibrolamellar bone, while those from pachycephalosaurids have
   radial vascularity."

  Adams, J. and C. L. Organ. 2005. Histologic determination of ontogenetic
    patterns and processes in hadrosaurian ossified tendons. _Journal of
    Vertebrate Paleontology_ 25(3): 614-622.

  "Development and metaplasia of ossified tendons in two hadrosaurine dinosaurs
   (*Maiasaura peeblesorum* and *Brachylophosaurus canadensis*) are described
   comparison with the known developmental processes of ossified tendons in
   turkeys (*Meleagris gallopavo*). Mineralized primary tendon tissue and
   replacement patterns suggest that ossified tendons in hadrosaurs grew
   initially in a manner similar to those of turkeys. That is,
   begins with apatite deposition and is followed by resorption of mineralized
   primary tissue and subsequent bone formation. Earlier ontogenetic onset of
   tendon ossification and later offset among ossified tendons of hadrosaurs
   differentiates them from tendons of turkeys. In addition, an external
   fundamental system (EFS) in hadrosaurian tendons indicates that they grew
   radially beyond the original tendon boundary, a process unknown among avian
   tendons. Tendon histology indicates that hadrosaurian ossified tendons
   developed in step with the skeletal system and that ossification was not
   induced by biomechanical stress."

  The abstracts of these two papers are pretty comprehensive, actually, so I
won't describe them in too much detail. Organ and Adams show that the "ossified
tendons" of dinosaurs really are ossified tendons, but that uniquely they are
perisotatic and retain vascular centers. The "tail rods" of the dromaeosaurids
*Deinonychus* and *Saurornitholestes* are argued to be ossified tendons, but
not neccessarily isolated from prezygapophyseal elongation, based on the
histology of the structures. The unique features of marginocephalian tendons
(an irregular central mass of oblate, oval, and circular globular structures of
haversian bone) differ from the regular structures of ornithopod tendons which
show regular circular and roughly the same size of haversian systems surrounded
by irregular periosteum layering, and from tendons sampled from
*Euoplocephalus* which show no trace of collagenous fibrous structures and even
exhibit LAGs. Subsequently, Adams and Organ show that hadrosaur tendons also
show LAGS and equate this due to the early onset of ossification in these
animals (using what Jon Wagner calls *Brachylophosaurus* for both genera as the
exemplar), unlike other dinosaurs or even birds, gators, and so forth. The
presence of the EFSs in hadrosaur tendons shows that periostatic growth occurs
after the establishment of tendon venous and nervous systems, and that growth
around these may incorporate a nutrient system as in avian tendon ossification

  These papers also show that the closest homologues to the dinosaurian tendon
vascular system is avian, as has been shown through various other bone
dissections and histology studies for the last three decades, but some people
don't get this evidence for a faster metabolism than crocs, or that bone growth
is determinate until a point, unlike most other reptiles and exhibits a
heightened growth period equivalent to homeothermic animals. The weight of
evidence cannot deter faith in sluggard, cold-blood dino-lizards, I guess.

  Salgado, L., S. Apesteguía, & S. E. Heredia. 2005. A new specimen of
   *Neuquensaurus australis*, a Late Cretaceous saltasaurine titanosaur from
   North Patagonia. _Journal of Vertebrate Paleontology_ 25(3):623-634.

  "A new specimen of the sauropod dinosaur *Neuquensaurus australis*, collected
   in the locality of Cinco Saltos (Patagonia, Argentina), provides an
   opportunity to improve out knowledge of the anatomy of this dinosaur. The
   elements represented in this specimen include a complete cervical vertebra,
   most of the dorsal vertebrae, fifteen caudal vertebrae, the complete sacrum
   articulated to both ilia, one ischium, two femora, one tibia articulated to
   the fibula and astragalus, and two osteoderms. Surprisingly, the sacrum is
   comprised of seven vertebrae, the last of which, unfused to the other size,
   is apparently biconvex. A third femur and one tibia were found associated
   with this specimen; these are morphologically similar but stouter than those
   belonging to the former specimen."

  They argue that *Neuquensaurus robustus* may be a junior synonym of *N.
australis* due to the presence of both robust and gracile morphs united in this
quarry and adjunct to one another (the more complete specimen, MCS-5 and
referred femur MCS-9). Additionally, and perhaps more fascinating, a biconvex
centrum is adhered to the sixth sacral and it's transverse processes are fused
to the poaterior ilia, indicating that it is a seventh sacral. The element
agrees in morphology to the first biconvex caudals of other titanosaurs, and
shows that this element may be incorporated in extra-hexate sacral systems, as
well as that the coding of the first caudal morphology of this animal will be
procoelous, notr biconvex, and this may mess with phylogenetic interpretations
unless homologues are taken into account (incorporated vertebrae, for example).
In addition to the abstract, the specimen MCS-5 also possesses caudal vertebrae
1-3 and 9-14, and other material collected from the same site includes a
scapula, humerus and metatarsal (MCS-7, 8, and 10, respectively).

  The authors diagnose *N. australis* thusly: "(1) Fibula with strong lateral
tuberosity and bent shaft[;] (2) anteriormost dorsal vertebrae lacking
centroprezygapohysal (cprl) and centropostzygapophyseal (cpol) laminae[;] (3)
seven sacral vertebrae; (4) sacral central 3 to 5 narrowed[;] (5) mid and
posterior caudal vertebrae bearing transversely wide, non-keeled ventral
depression, limited by lateral rounded ridges culminating in articular facets
of hemapophyses[;] and (6) lateral walls of caudal vertebral centra little
exposed in ventral view[.]"

  Complex internal secondary and tertiary diverticula in the lateral
pleurocoels of anterior dorsals are also illustrated, showing a more camarate
and not nearly so simplistically camellate internal structure that,
undoubtedly, grades into a camellate internal structure. Meanwhile, the femoral
morphs show that they are consistent with *N. robustus* and that the likelihood
of these two taxa being separate species is extremely unlikely, though while
von Huene erected the species differences to make note of this distinction of
robusticity, Powell (1986) rejected the hypothesis, and the current authors do
not take sides. I think the data is pretty consistent.

  Also in this isse, Gerald Mayr (_JVP_ 25(3):635-645) reviews *Messelastur*
and performs a cladistic analysis using 110 characters and 23 taxa, and finds
that it is the sister taxon to the Wyoming Green River "raptor" *Tynskya
eocaena* based on "(1) beak short and raptor-like; (2) well-developed processus
supraorbitalus present; (3) mandible with very deep rami; (4) proximal end of
humerus without foramen pneumaticum; (5) tibiotarsus without ossified pons
supratendinous; (6) tarsometatarsus with well-developed cristae hypotarsi
bordering a wide sulcus; (7) trochlea metatarsi II small; (8) trochlea
metatarsi III very broad; (9) and trochlea metatarsi IV plantarly inflected."
These are used to diagnose the new "family" Messelasturidae.

  The last few features related to the zygodactylous pes of owls, as well, and
may optimize as features shared with Strigiformes, which is found to be the 
sister taxon of Messelasturidae based on "distal end of tibiotarsus without
ossified pons supratendinous" and "trochlea metatarsi III very broad; (9) and
trochlea metatarsi IV plantarly inflected". This means Messelasturidae is
actually diagnosed by fewer than the 9 characters listed, which show up in a
more inclusive clade.

  Mayr also finds that Falconiformes is the sister taxon to the
messelasturid-strigiform clade by "tarsometatarsus, hypotarsus without body
canals, crista lateralis separated from crista medialis by a wide sulcus" and
"osseous claws, pair of canals lateral and medial to tuburculum flexorum" (both
of these are noted as absent in *Messelastur*, but are present in *Tynskya*).

  Mayr's tree, with 343 steps and a CI of 0.36, provides the following

     |  |--Musophagidae
     |  `--Cariamidae
           |  `--+--Sagittariidae
           |     `--+--+--Falconidae
           |        |  `--Accipitridae
           |        `--+--Messelasturidae
           |           `--Strigiformes
              |  `--Columbidae
                       |  `--+--Steatornithidae
                       |     `--Trogonidae

  Note that both Falconiformes and Gruiformes are paraphyletic in regards to
first strigiforms, and to other "land birds", respectively, and that
Strigiformes is restricted to owls, hummingbirds, and the nightjar/goatsucker
clan, with other "strigiforms" united with psittaciformes and colies.

  Raynoso V.-H. 2005. Possible evidence of a venom apparatus in a Middle
   Jurassic sphenodontian from the huizachal red beds of Tamaulipas, Mexico.
   _Journal of Vertebrate Paleontology_ 25(3):646-654.

  Raynoso describes a new sphenodontine sphenodontid, naming it *Sphenovipera
jimmysjoyi*. Note that the specific name is intended to be pronounced as
"he-mis-joyee", and is named to honor the Jim's Joy locality of Huizachal
Canyon, Municipio de Ciudad Victoria, Tamaulipas, México, which was buried by
overburden during the construction of the Tula--Ciudad Victoria Highway, and
thus lost forever. The generic name needs no introduction, I don't think.

  The taxon is represented by that most ubiquitous of all sphenodontian bony
parts, a lower jaw (in this case, a right mandible), IGM 6076, which while
preserving the fused teeth and saw-like structure of the jawbone, also bears
two long conical crowns near the symphyseal joint that bear distinct mesial
grooves. The mandible is also strongly elongated in the dentary versus the
postdentary region, showing shortening of the latter, a feature that Reynoso
links to venomous snakes, giving attention to the xenodontine colubrid
*Alsophis* versus non-venomous colubrids. This jaw structure is linked to the
extension of the lower jaw in gaping without elongating the mandibular
adductors by posterior retraction of the insertion points, but also weakens the
jaw bite, which are favorable towards a venomous bite. Reynoso also hows that
*Pleurosaurus* also shows a similar mandibular arrangement, but which lacks the
grooved teeth, as well as other basal sphenodontians. Correlates with
power-biting in sphenodontians due to enlarged pterygoid flanges is not
testable due to the specimen's restriction to a mandible.

  Also in this paper is a review of *Platypterigius hauthali* based on a review
of the holotype forefins (all that is known, and described by von Huene in 1925
and 1927) from Fernández and Aguirre-Urreta (_JVP_ 23(3):583-587).

  Additionally, a review of *Mauisaurus haasti* from Hiller, Mannering, Jones
and Cruickshank (_JVP_ 23(3):588-601) from New Zealand based on a new specimen
with a nearly complete axial colum which argues that it cannot be synonymous
with *Tuarangisaurus keyesi* (yet). Notably, *Mauisaurus* specimens showing a
monospecific genus, are known from the middle Campanian into the lower and
upper Maastrichtian, though less than halfway up the Maastrichtia levels.
Another example of a CampanoMaastrichtian predator!


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

Yahoo! Music Unlimited 
Access over 1 million songs. Try it free.