The deep-tailed swimmer emerges from the lake...

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

Greetings,

A long-awaited paper is finally out:
Colbert, E.H. & P.E. Olsen. 2001.  A new and unusual aquatic reptile from
the Lockatong Formation of New Jersey (Late Triassic, Newark Supergroup).
American Museum Novitates 3334: 1-24.

This is the paper that finally describes _Hypuronector limnaios_, the
deep-tailed swimmer of the lake.  This is an eastern North American
drepanosaurid, long known in the literature from a little drawing in some of
Paul Olsen's various publications on the Newark Supergroup and its fauna.
Don Baird is credited with creation of the name.

_Hypuronector_ is known from twenty or more specimens from the Late Carnian
Lockatong Fm. (about 220 Ma), ranging from ends of limb bones to a partially
articulated skeleton lacking a skull.  It adds a lot to our knowledge of
drepanosaurid anatomy, including confirmation that drepanosaurids were a
rather morphologically diverse lot.

No cranium is known.  Mandibles have an edentulous tip and six or more
simple pointed teeth with pleurodont or subthecodont implantation.  There is
no mandibular fenestra.  Cervicals are proportionately shorter but generally
similar to those of _Megalancosaurus_.  It lacks the massive expansion of
the pectoral neural spines.  As the name implies, the chevrons are
exceedingly long (fifteen or more times centrum depth).  Scapulocoracoid
region is very similar to _Megalancosaurus_, as is the forelimb.  The manus,
however, seems less specialized than that of _Megalancosaurus_.  The pelvis
is nearly identical to _Megalancosaurus_; the hindlimb is similar to, but
more slender than, those of _Megalancosaurus_ or _Drepanosaurus_.  The foot
is poorly preserved, but seems less specialized than _Megalancosaurus_.

Based on the proportions of the tail, Colbert & Olsen interpret this critter
as a swimmer.  The do not see any sign of great mobility at the base of the
tail that would allow it to be raised up, so they do not consider it a
likely tree-climber.

P.S. For those interested, John Merck has had his metaphorical nose to the
phylogenetic grindstone this summer, so hopefully he'll have his (greatly
expanded!) archosauromorph paper submitted within the next six months.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796