A newarceoscelid
reptile,
Zarcasaaras
tanyderus,
(Lower
fromtheGutler
Formation
Permian)
of north-central
NewMexico
byDonald
B. Brinknan,
Curator,
Tyrrell
Museum
of Palaeontology,
Drumheller,
Alberta,
DavidS Berman,
Associate
Section
of Vertebrate
Fossils,
Curator,
Carnegie
Museum
oi Natural
History,
Pittsburgh,
PA,and
David
A. Eberth,
Graduale
Student,
Department
Toronto,
0ntario
ol Geology,
University
of Toronto,
A new genus and species of araeoscelid
reptlle, Zarusaurus tanuderus, is described
on the basisof a partiai jaw and disarticulated postcranial elements from the Cutler
Formition (Lower Permian) of north-central New Mexico. It is the first reoresentative of this family to be reported from that
state, and it is considered closely related to
Araeoscelis.Z. tanyderus possesses a combination of primitive and derived features
with respeci to Araeoscelis, indicating that
they could not have had a direct ancestordescendant relationship.
Introduction
The phylogeneticpositionsof Araeoscelis
and
Petrolacosaurus
are important to our understanding of the early diversificationof diapsid reptiles.Araeoscelis
is a small,lightly built
reptile from the Lower Permianof Texasand
Oklahoma (Vaughn, 1955;Simpson, 1979).
In the most recent detailed descrintion of
Araeoscelis,
Vaughn (1955)concluded that it
is best considereda lizard-likeexperimentof
the anapsid captorhinomorph reptiles. He
argued that, exceptfor such featuresas the
upper temporal fenestra,specializeddentition, elongatelimbs, and elongate cervical
vertebrae,Araeoscelis
resemblesin most respectsthe primitive membersof the group.
On the basis of better preservedearly captorhinomorphs, Carroll (1959)agreed wiih
Vaughn's assessment.Romer (1956, 1966,
1967),on the other hand, placed Araeoscelis
with a number of poorly known, early (Permian and Triassic) forms generally referred
to as protorosaurs,which he regardedas ancestralto the sauropterygians(plesiosaurs,
nothosaurs,and placodonts).The protorosaurs,as definedbv Romer,arenow believed
to be a ratherdiverseassemblage
of distantly
related forms (Kuhn-Schnyder, 1967; Brinkman, 1981;Chatterjee,1980;Carroll, 7981),
and there is little evidence to suggest that
Araeoscelis
is closely related to any of them
(Vaughn, 1955).
The controversyof the phylogeneticaffinities of Araeoscelis
has seemingly been resolved with the demonstration of its close
relationship with Petrolacosaurus,
a diapsid
reptile of lizard-likeproportions from the Late
Pennsylvanianof Kansas.Petrolacosaurus
was
originally describedby Peabody(1952),who
believedit to be closelyrelated to the eosuchians,the most primitive group of diapsid
reptiles, with strong ties with the captorhinomorphs.Vaughn (1955)recognizedthe close
similarity between Araeoscelisand Petrolacosaurusand even suggestedthat they may beIong to the same family, thereby implying
May 1984 Nau MexicoGeology
that Petrolacosaurus
was related to the cap- skull, and are interpreted as an adaptation
torhinomorphs.It alsohas beenarguedthlt
to a specializeddiet that probably included
Petrolacosaurus
belongsto a group of archaic invertebratesprotectedby a heavy exoskeledaphosaursof the early mammal-like rep- eton. Most importantlv this theory is extile pelycosaurs(Stovall, Price, and Romer, tendedto suggestthat the absenceof a lower
may be the
1956).Most recently, a redescription of Pe- temporal fenestra in Araeoscelis
trolacosaurus
bv Reisz0.977, 1981\has estab- result of a secondaryclosure.Theseconclulishedfirmly 6oth its positionas a primitive sions prompted a somewhat revised classiwas assignedto
diaosid and its close relationship with Ar- fication in which Araeoscelis
aeoicelis.
Previouslyundescribedspecimens the AraeoscelidaeWilliston, 1910, and PetroPeabody,
to the Petrolacosauridae
of Araeoscelis
presently under study (Reisz, lacosaurus
Berman,and Scott,in preparation)have pro- 1952;both families were united under the
vided additionalinformation that greatly ex- suborderAraeoscelidiaWilliston, 1913.Other
p a n d s u p o n o u r a s s e s s m e n t o f t h e generathat have been included in this suba order, but which are consideredtoo poorly
phylogenetic relationships of Araeoscelis,
summary of which can be given here. Cur- known to be assignedto either famiiy, ar-e
shares I(adaliosaurusCredner, 1889, and Dictybolus
rent evidenceindicatesthat Araeoscells
a more recent common ancestorwith-that
Olson, 1970.
is, it is more closelyrelatedto--Petrolacosau- The new araeosceliddescribedherc as Zarrus than with the captorhinomorphs,and that casaurustanyderusconsistsof a partial, disboth genera share a more recent common articulatedskeletoncollectedby the authors
ancestorwith eosuchiansthan with the cap- during the summer of 1982from the Cutler
torhinomorphs.
Formation (Lower Permian) near the village
Together, Araeoscelisand Petrolacosaurusof Arroyo del Agua in Rio Arriba County,
representthe earliest,most primitive known north-centralNew Mexico (Fig. 1). The disstagein the adaptiveradiationof the diapsid covery was reported in a preliminary paper
reptiles. This relationship is strongly sup- on the sedimentology and paleontology of
ported by their postcranialskeletonsthat ex- the Lower Permianred-beddepositsof northh i b i t o n l y m i n o r d i f f e r e n c e s ,b u t , m o s t central New Mexico (Eberth and Berman,
importantly, they share numerous derived 1983).Z. tanyderusrepresentsthe first record
feafures.Cranial differencesbetween the two of an araeosceloidfrom New Mexico. It is
than to Pegenera,on the other hand, are more marked. more closely related to Araeoscelis
They are recognizedas providing Araeoscelis trolacosaurus
and is, therefore, assigned to
with a more massive, sturdily constructed the Araeoscelidae.
L--.-FIGURE l-Locality
of Zarcasnurustanyderus,Rio Arriba County, north-central New Mexico.
Systematicpaleontology
Class Rsprrlre
SuborderAnaeoscrlron Williston, 1913
Family AnaroscEuoanWilliston, 1910
Zanceseunus, new genus
tanyderusnsp.
Tvpr spnclss:Zarcasaurus
Eryuor-ocv-Refers to the Agua Sarca, a
smallcreekabout 3 km northwest of the type
locality;pronouncedZarcaand spelledas such
on early maps and publications (Langston,
of an ancient river svstem. The limited extents of the crevasse channels suggest the
proximity of interchannel pond and./or marsh
environments where such channels would
quickly lose their U-shape morphology.
DIacNosrs-Same as for the genus.
Description and comparison
TABLE 1-Measurements (in mm) of vertebrae of
tanyderusgen. et sp. nov., CM 47704.
Zarcasaurus
f. is the greatestlength of centrum, 2 is the height
of the centrum at the anterior end, 3 is the transversewidth of the centrum at the anterior end, 4
is the height of the centrum at the posterior end,
5 is the transverse width of the centrum at the
posterior end, and 5 is the length of the neural
arch pedicle.
All of the elements assigned to the holoVertebra
type, CM 41704,werc collected from the sur1es3).
face and had eroded out of a single slope.
7.5
2.8 3.5
Axis
DracNosrs-A small araeoscelid closely re- Although only two elements (dorsal verte77.2 4.0 4.6 3.5 3.8 8.5
Midcervical
lated to Araeoscelisand characterized by the brae) were articulated, all the elements were
Posteriorcervical 8.6 3.5 3.7 3.1 3.9 4.3
following derived features: cervical verte- found closely associated. None of the parts
5.9 2.8 3.9 3.2 3.9 3.4
Dorsal
5.0 3.4 3.5 3.3 4.0 3.4
brae are longer, with central lengths exceed- is duplicated and all are of an appropriate
Dorsai
ing those of the dorsals by as much as two
size to have belonged to a single individual.
times; absence of a prominent notch on the No bones were found associated with CM
distal edge of the astragalus that separates 41704 that would indicate the presence of
the articular facets for the fourth distal tarsal another form of similar size. For these reatentative, as is identification of the preartiand centrale. Primitive features that distin- sons, CM 47704is considered to represent a
cular-angular contact near the ventral margdsh Zarcasaurusfrom Araeoscelisinclude: the single individual that probably was repregin of the jaw fragment. In its possession of
humerus lacks ectepicondylar foramen; a sented originally by a greater part of artica precoronoid, Zarcasauruswould more closely
supracondylar process is present on the pos- ulated skeleton.
approach Araeoscelis than Petrolacosaurui.
terior condyle of the femur; a concave area
Lowrn 1ew-The lower jaw is represented
There is no evidence of a postsplenial in Zarof finished bone separates the lateral and me- by a short section of the left ramus just ancasaurus.The postsplenial is absent in Ardial articular surfaces on the proximal end terior to the adductor fossa (Fig. 2). It inaeoscelis.but is present in Petrolacosaurusas
of the tibia; the tibial facet of the astragalus cludes the posterior end of the dentary, which
a moderate-sized element wedged between
is convex and not developed into a ridge- includes one emptv socket and two incomthe angular and prearticular at the level of
and-trough pattern.
plete teeth. The more complete tooth is missthe coronoid.
ing only its tip; this is possibly a result of
VnnrpnnaE-Three cervical and five dorsal
Zarcasaurus tanyderus, new species
wear. The tooth is stout, like those of 4rvertebrae of varying degrees of completerather than like the slender teeth of
ness and fragments of centra comprise the
Ervrr.rorocv-Derived
from the Greek tany, aeoscelis,
though it lacks the lateral, invertebral elements. Two of the dorsal verlong, and deros, neck, referring to the spec- Petrolacosaurus,
cipient cusp seen in the cheek teeth of Artebrae were preserved in articulation. The
imen's very long cervical vertebrae.
three cervicati Gig. 3A-C) include an axis,
Holorypr-CM
41704 (collections of the aeoscelis.Little of the bases of the teeth can
midcervical, and posterior cervical. DeterCarnegie Museum of Natural History, Sec- be seen in the lateral view of the jaw due to
teeth
on
the
low
level
of
implantation
of
the
mination of their serial positions has been
tion of Vertebrate Fossils) is a partial, disthe medial surface of the dentary. In this feabased on successive changes in the cervical
articulated skeleton consisting of the following
series of Arneoscelis and Petrolacosaurus.
elements: a short section of the left ramus of ture, Zarcasaurus mote closely approaches
As in Araeoscelis and Petrolacosaurus, the
the lower jaw just anterior to the adductor Petrolacosaurusthan Araeoscelis.
Identification of the sutures on the lateral
cervical vertebrae of Zarcasaurusare conspicfossa; three cervical, including axis, and five
dorsal vertebrae, and fragments of centra; surface of the jaw fragment presents no se- uously elongate. The centrum of the midthe distal ends of both humeri; the proximal rious problems. However, with the excep- cervical, the longest and most complete of
the three cervicals, is 1.9 and 2.2 times the
and distal ends of the left femur and a fras- tion of the coronoid, the interpretation of the
length of the longest and shortest of the prement of the proximal end of the right femui; sutures on the medial surface is uncertain.
served dorsals (Table 1). The neural spine,
the proximal and distal ends of both tibiae; Though the coronoid of Zarcasaurusis incomnearly preserved in its entirety only in the
the left astragalus; several metapodials and plete, its relative depth, as in Araeoscelis,was
p h a l a n g e s ; a n d n u m e r o u s i n d e t e r m i n a t e obviously much greater than in Petrolacosau- midcervical. is verv low. In the axis ahd midras. Identification of a narrow splint of bone
cervical vertebrae, the pedicle of the neural
fragments.
contacting
the
anterior
end
of
ihe
coronoid
arch extends about three-fourths of the length
Honrzol AND LocALITv-Cutler Formation (Lower Permian: Wolfcampian), about 1 as the anterior coronoid, or precoronoid, is
km southeast of the small village of Arroyo
del Agua in Rio Arriba County, north-central
New Mexico (exact locality data on file at the
Carnegie Museum of Natural History). The
holotype, as is the case with the majority of
vertebrate fossils from the Cutler Formation
of the Arroyo del Agua area, is from the extensive, well-known deposits commonly referred to as lake or pond deposits (Langston,
1953). Preliminary investigations of these
deposits (Eberth and Berman, 1983), as well
as adjacent lithofacies, have revealed that they
are discrete, U-shaped bodies of interbedded
mudstones and minor sandstones and have
a very limited extent. Their close lateral association with U-shaped, low-sinuosity
rcM
channel fills consisting of vertically accreted,
medium to coarse sandstones more properly
A
is
the medial and B is the lateral view
47704.
sp.
nov.,
CM
FIGURE 2-Zarcasaurus tanyderus gen. et
suggests that they are actually remnants of
of a portion of the left mandible; angular (A), coronoid (CO), anterior coronoid (COA), dentary (D),
crevasse channel fills in an anastomosed reach
preaiticular (PRA), and surangular (SA) indicated.
Nm Mexico Geology May 1984
of the centrum, and in the posterior cervical
the pedicle is restricted to the anterior half
of the centrum.The zygapophysesof the axis
and midcervicalare narrowly separatedand
extend very little beyond the lateral margin
of the centrum. The axial prezygapophyses
are much smallerthan those of the midcervical, facenearly as much laterallyas dorsally,
and the facetsare convex. The prezygapophyses of the midcervical extend beyond the
end of the centrum, whereas the postzygapophysesdo not. At the base of the neural
arch, there is a shallow, Iateral excavation.
The anterior ends of the centraare strongly
beveledto accommodatethe intercentra(not
found); in the axis, this featurehas been exaggeratedby breakage.The transverseprocessesof the axis and midcervicalvertebrae
consistof a very small, horizontal ridge near
the anterior end of the centrum; a small costal facet is present near the anterior end of
the process.The transverseprocessof the
posterior cervical differs from the more anterior vertebraein severalfeatures:its base
extendsposterodorsallyfrom the anterior rim
of the centrum to the midlength of the base
of the neural arch; it extends much farther
laterally; and the length of the costal facet is
nearlyequalto that of the baseof the process
and expandssomewhatposterodorsally.The
ventral longitudinal keels of the axial and
midcervicalcentraare V-shapedin crosssection, whereas that of the posterior cervical
is U-shaped.
Severalfeaturesdemonstratethat the cerv- man, and Scott, in preparation) and Petro(Reisz,1981),but in other Paleozoic
ical vertebraeof Zarcasaurus
more closelyap- Lacosaurus
proachthoseof Araeoscelis
(Fig.3D) than those tetrapodsas well (Vaughn, 1970).The dorsal
(Fig.3E). The most notice- neural arches of Zarcasaurusand Araeoscelis
of Petrolacosaurus
able feature is that the neural arch pedicles differ from those of Petrolacosaurus:
they are
of the axis and midcervicalvertebraeof Zar- slightly wider, have a somewhatswollen apcasaurusand the cervicals of Araeoscelisex- pearance,and they possessmuch lower neural
tend for about three-fourthsof the length of spines.None of the neural spinesshow any
the centrum. In PetrolacosaLffus,
on the other signsof the mammillary processesthat have
(Vaughn, 1955)
hand, the pediclesof all the cervicalsare re- been described in Araeoscells
(Reisz, 1981).The neural
stricted to the anterior half of the centrum, and Petrolacosaurus
as in the posterior cervical of Zarcasaurus. archesexhibit prominent lateralexcavations.
The cerviial zygapophysesdiverge more The zygapophysesare smaller than those of
widely and extendmore laterallybeyond the the cervicalsand extend very little beyond
margin of the centrum inPetrolacosaurus
than the lateral margin of the centrum. The prein Zarcasaurus
or Araeoscelis.
The neural spine zygapophysesextend only to the anterior end
of the midcervical of Zarcasaurus,as in the of the centrum, whereas the postzygapocervicalsof Araeoscelis,
is little more than a physesextend beyond the posterior end. The
low ridge, whereas in Petrolacosaurus,
the zygapophyseal planes diverge only slightly
cervicalspinesare moderatelyhigh and blade- from the horizontal. The small transverse
Iike.
processesare situatedjust below the baseof
(Fig. the prezygapophysesnear the anterior rim
The dorsal vertebrae of Zarcasaurus
3E), as in Petrolacosaurus
and Araeoscelis,are of the centrum and project only a short disconsiderablyshorter than the cervicals.The tance laterally. The elongate axis of the base
lengths of the centra are about equal to, or of the process,as well as its costal surface,
slightly lessthan, the widths. With the marked is inclinedabout 45"from the horizontal,and
exceptionof an isolatedneural arch, the height neither the processnor its costalsurfaceexof the dorsalneural spinesis far greaterthan hibit any signs of a capifular-tubercular dithat of the midcervical.The differencein spine vision. There is no beveling of the ventral
height of the dorsalvertebraemay be a result rim of the anterior and posterior ends of the
of gradual changealong the column or of a centra to accommodatethe intercentra(not
regular pattern of alternation in height of found). The ventral halves of the centra are
successive
spines;the latter featurehas been laterallycompressed,forming a narrow, venreported not only in Araeoscelis
(Reisz,Ber- tral, longitudinal ridge that is U-shaped in
crosssectron.
ApprxorculaR ELEMENTS-Preservedelements of the appendicularskeletoninclude:
the distal ends of both humeri; the proximal
\and distal ends of the left femur and a frag\4!
T\
ment of the proximal end of the right femur;
U
the proximal and distal ends of both tibiae;
the ieft astragalus;and isolatedmetapodials
and phalanges.The terminology used in orienting the hindlimb elements is that proposed by Rewcastle(1980).
The humerus of Zarcasaurus
(Fig. 4), as in
Petrolacosaurus
and most primitive reptiles,
a well-developed,distally-directed
possesses
supinator process which in dorsal view is
\-^
\
-r separatedfrom the ectepicondyleby a deep
E \ -i-ectepicondylargroove. Both the supinator
process and ectepicondyleare covered by
finished bone, indicating a late adult stage
of developmenl.In Araeoscelis
the ectepicondylar groove is bridged over distally to form
the ectepicondylarforamen.fust distal to the
supinator processa prominent, hemispherF^
ical radial condyle projects ventrally and
l:\
slightly distally from the distal margin of the
.::x:..:.. . |/
(
numerus.
:"|o/
Enough of the femur is represented to in\
.{
1.,
dicate that it was very slender (Fig. 5). For
.
Ii:
\
most of its length the shaft is subcircular in
f ::rti;;;i' 3
crosssection.The proximal end of the femur
is turned strongly upward, and the entire
bone probably had a pronounced sigmoidal
flexure. In this feature and in its.slenderproand C is the posterior cervical vertebrae of Zarcasaurus portions, the femur of Zarcasaurusis more
FIGURE 3-A is .n"
than Petrolacosaurus.
As
nov., CM 41704,in lateral, dorsal, and ventral views; D and E are diagrammatic like that of Araeoscelis
tanyderusgen. et sp. "o;*3;;;1,
but in contrast Io Araeos(after Vaughn, 1955)and Petrolacosaurusin Petrolacosaurus,
lateral views (not to scale)of posterior cervicals of Araeoscelis
(after Reisz,1981),respectively;F are lateral views of dorsal vertebrae(relative serial positions unknown) celis,the adductor ridge does not terminate
of Z. tanyderus.
proximally in a distinct internal trochanter;
ffi\
\t.'.+{
A--
€il
dhr
\#
-c\
May 1984 New Mexico Geology
--<-\
\ ,t1
and Petrolacosaurus.
Of the
seenin Araeoscelis
rather, the adductor ridge, which is repre- of the tibia is divided into two areas-a flat,
sentedon the shaft of the femur by a faintly lateral area and a convex, ventrally project- isolated phalanges, one is strongly curved
visible line, extends proximally as a sharp ing, mesial area-that are separatedby a and claw-like.
crest along the anterior bounding ridge of shallow groove.A similar arrangementis seen
Discussion
the intertrochantericfossa.The length of the in Araeoscelis
and Petrolacosaurus.
tanyderus
as
intertrochanteric fossa is greater than the
The assessmentof Zarcasaurus
The left astragalus(Fig.D is complete,and
width of the femur head. This compareswell the L-shape is typically reptilian, although a member of the suborder Araeoscelidiais
with Araeoscelis,
but differs from Petrolacosau- the neck is short. The astragalusof Petrola- basedon its elongatecervicalvertebrae,latrus where the two measurementsare about cosaurus
is alsoL-shaped,but the neck is much eral excavationsof the neural arches, the
equal. As in primitive reptiles generally,a longer; in Araeoscelis
it is not L-shaped, al- structureof the distal articular surfaceof the
distinct ischiotrochanterictuberosityis pres- though the neck is similarly short. A notch tibia, and the long, slender proportions of
ent near the posterior margin of the dorsal near the distal end of the calcanealarticular the limb elements.All of these featuresare
The
and Petrolacosaurus.
surfaceof the femur head.
surfaceforms the mesial portion of the per- sharedby Araeoscelis
The dorsal surfaceof the distal end of the forating foramen.The distal articular surface astragalusis the only element that does not
femur is markedby a deepintercondylarfossa. of the astragalusis divided subequallyinto conform to the basic structural pattern of the
Apart from this, the holotype
The dorsal surfaceof the posterior condvle a lateral (fibular), convex, condylarJike area araeosceloids.
extendsdistally a short distancebeyond the and a mesial(tibial), concave,socket-likearea. does not possessany features that would
prevent its assignmentto the suborder.
level of the tibial facetbelow it as a distinct, Presumablythe convexareaarticulatedwith
It is clear from the previous section that
liptike process,here termed the supracon- the fourth distal tarsal,and the concavearea
more closelyapproachesAraeosdvlar process.A narrow strip of finished bone, articulatedwith the centrale.This arrange- Zarcasaurus
in overall structure.
continuouswith that of ihe intercondylar ment is unlike the condition in either .4r- celisthan Petrolacosaurus
fossa,separatesthis processfrom the tibial aeoscelis
where a notch in Among the more important featuresshared
or Petrolacosaurus,
but absent in
facet. Ridges on the dorsal surface of the the distal edge of the astragalusseparatesa by Zarcasaurusand Araeoscelis,
are the shapeand position of
supracondylarprocess mark the site of at- Iateral condyloid process(the articular sur- Petrolacosaurus,
tachmentof the extensormusculatureof the facefor the fourth distal tarsal)from a mesial the cnemial crest of the tibia, the presence
lower leg. In contrast to Zarcasaurus,
the in- convexarea(the articular surfacefor the cen- of stout teeth, and the great length of the
t e r c o n d y l a r f o s s a i s s h a l l o w e r , a n d t h e trale). The tibial articular facet of the astra- pedicles of the cervical neural arches. The
supracondylarprocess is absent in Araeos- galusof Zarusaurusis a simple convexsurface, former two feafuresare interpreted as shared,
celis.The intercondylarfossaof Petrolacosau-with no ridge-and-trough pattern like that
rus is well developed. Although the femur
figuredby Reisz(1981,fig.22) doesnot show
a supracondylarprocess,an extensivearea
of unfinished bone at this site may indicate
that its absenceis due to the immaturity of
the specimen.The popliteal areaon the ventral surfaceof the distal end of the femur is
a smooth,broadly concavedepression.As in
/ r'1'''':
Araeoscelis,
the posterior limited ridge of the
/ .,!
popliteal areais low; in Petrolacosaurus
it is a
relatively high, sharp crest.
The oroximal articular surfaceof the tibia
(Fig. 6i is triangular in outline with a large,
oval-shaped, lateral articular surface for the
posterior (fibular) condyle of the femur and
a small, mesial articular surface that faces
somewhat laterally and posteriorly for the
anterior (tibial) condyle of the femur. The
RAD
anterior corner of the proximal end of the
tibia forms a knob-shapedcnemialcrestsimilar to, but lessstrongly developedthan, Araeoscelis;
the tibia ofPetrolacosaurls
lackssuch
a crest. Between these three areas of the
proximal articular surfaceis a deep, concave
area of finished bone. A similar area of finished bone has not been described in Araeoscelis,
nor has it been observed in those
Araeoscelis
specimensexamined during the
courseof this study that are presumed to be
adults on the basis of the complete ossification of their skeletons.The proximal articular surfaceof the tibia of Petrolacosauruslnas
not been describedin detail. The preserved
proximal ends of the tibiae of Zarcasaurus
suggest that the bone is concave laterally.
I
This is a primitive feature seenin Petrolacosaurus and primitive reptiles generally, but
not in Araeoscelis
where the great elongation
of the limbs has resulted in the tibia being
ICM
straight or slightly concavemedially. A ridge
on the lateral surfaceof the tibia presumably FIGURE l,-lsyg45su7y5 tanyderus gen. et sp. nov. Dorsal and ventral views of distal ends of the right,
marks the site of attachmentof the interos- A, and the left, B, humeri; ectepicondyle (ECT), ectepicondylar groove (ECT GR), radial condyle (RAD),
seousligament. The distal articular surface and supinator process (SUP) indicated.
Neu Mexico Geology May 1984
derived characters and, therefore, underscore the close relationship between Zarcasaurus and Araeoscelis.Zarc'asauruspossesses
several features that are widespread among
primitive reptiles and can be considered
primitive with respect to the condition in
Araeoscelis:there is no ectepicondylar foramen on the humerus; a distinct supracondylar process on the posterior condyle of the
femur is present; a concave area of finished
bone separates the lateral and medial articular surflces on the proximal end of the tibia;
and the simple tibial facet of the astragalus,
which is a convex surface lacking a ridgeand-trough configuration, is present. An additional feature that may be considered
primitive within the Araeoscelidia is the absence of a distinct internal trochanter of the
femur. This character state is not typical of
primitive reptiles, but is present in Petrolacosaurus,which in other respects is considered to be the most primitive member of the
suborder Araeoscelidia (Reisz, Berman, and
Scott, in preparation).
Zarcasaurusexhibits two derived features
not seen in either Araeoscelisor Petrolacosauras. One is the great length of the cervical
vertebrae of Zarcasaurus, the centra of which
are as much as two times longer than the
dorsal centra, whereas in Araeoscelisthe maximum is 1.61 times (Reisz, Berman, and Scott,
-1.55
in preparation) and in Petrolacosaurus
times (Reisz, 1981). The second derived feature of Zarcasaurusis the structure of the distal articular surface of the astragalus. The
astragali of Petrolacosaurusand Araeoscelis,as
in Captorhinus(Peabody, 1951), have a deep
notch in the distal articular border. This notch
separates a condyloid-like structure at the
laterodistal corner of the astragalus from a
convex surface mesial to this. The distal notch
corresponds to the suture between the proximal fourth centrale and the tibiale of the
amphibian tarsus (Peabody, 1951). The ab-
sence of the distal notch in Zarcasaurus is
therefore viewed as a derived character. Although closely related to Araeoscelis,the existence in Zarcasaurusof both primitive and
derived features with respect to Araeoscelis
rules out the possibility ihat they had an
ancestor-descendant relationship.
It is worth noting that araeosceloid remains may be present among the isolated
limb elements described by Reisz (1980)from
the Early Permian at Fort Sill, Oklahoma,
and referred by him to the Protorothyrididae. This assessment was made solely on the
basis of primitive features, particularly the
presence on the humerus of a prominent,
CNEM
CNEM
I ST R
INT FCS
ICM
FIGURE 6-Left tibia of Zarcasaurus tanyderus gen.
et sp. nov. A are the posteromedial and articular
surface views of the proximal and distal ends, B
are the anterior and alticular surface views of the
proximal end, and C are the posterolateral and
oroximal articular surface views of the proximal
and distal ends; cnemial crest (CNEM) i;dicated.
n#eh
,
FIGURE S-Left femur of Zarcasaurus tanyderus gen. et sp. nov. A is the anterior view of the proximal
end; B is the dorsal view and C is the ventral view of the proximal and distal ends; adductor crest
(ADD CR), intertrochanteric fossa (INT FOS), ischiotrochaniericus tuberosity (IS TR), popliteal area
(POP), and supracondylar process (SC PR) indicated
May 1984 Nrw Mexico Geology
rc!
FIGURE7-Left astragalusoI Zarcawurustanyderus
gen. et sp. nov. A is the medial, B is the anterior,
C is the lateral, D is the posterior, and E is the
distal view; articular surface for centrale (CENT),
articular surface for fibula (FIB), articular surface
for tibia (TIB) indicated.
distally-directed supinator process located just
proximal to the radial condvle. Reisz noted
that th" Fort Sillhumerus and femur are surprisingly similar to humeri and femora of
Petrolacosaurusand Araeoscells,but he rejected their assignment to an araeoscelid because in the protorothyridids, as in the Fort
Sill elements, the epipodials are considerably
shorter than the propodials, whereas in Petrolacosaurus and Araeoscelisthev are subequal in length. This comparison, though
valid, cannot be applied here with any confidence because there is no assurance that
the Fort Sill limb bones are from individuals
of equal size, or that they represent a single,
or even closely related, species. On the other
hand, the very slender proportions of the
humeri and femora of the Fort Sill form, Petrolacosaurus,and Araeoscellscan be considered a shared, derived characterthat sets them
apart from the protorothyridids. The possibility that some of the Fort Sill limb elements
described by Reisz may pertain to an araeosceloid is reinforced by Carroll's (1968)
description of an isolated parietal from the
same deposit that indicates the presence of
a well-developed, upper temporal opening.
In retrospect, his conclusion that this parietal
may belong to a form structurally, if not phylogenetically, intermediate between primitive captorhinomorphs and eosuchians now
appears even more plausible.
AcxNowlrocunNrs-We
wish to thank Dr.
W Langston and Dr. P. Vaughn for reading
this paper and making many useful comments leading to its improvement. Field work
was supported by grants from the New Mexico Bureau of Mines and Mineral Resources
(to D. S B. and D. A. E.) and by the M.
Graham Netting Research Fund through a
grant from the Cordelia Scaife May Charitable Trust (to D. S B.).
References
Brinkman, D B , 1981, The origin of the crocodiloid tarsi
and the intenelationships of thecodontian archosaurs:
Breviora, no 466, pp 1-23
Carroll, R L , 1.968,A ?diapsid (Reptilia) parietal from
the Lower Permian of Oklahoma: Postilla, no 112, pp
1.-7
-,
1969,A Middle Pennsylvanian captorhinomorph,
and the intenelationships of primitive reptiles: Journal
of Paleontology, v 4, pp 1,51.-770
-,
7987, Plesiosaur ancestors from the Upper Permian of Madagascar: Royal Society of London, Philosophical Transactions, Ser B, v 293, pp 315-383
Chatterjee, S ,1,980,Malerisarlrs, a new eosuchian reptile
from the Late Triassic of India: Royal Society of London,
PhilosophicalTransactions, Ser B, v 291,,pp 163 200
Credner, H , 1889, Die Stegocephalen und Saurier aus
dem Rothliesenden des Plauen'schen Crundes bei
Dresden, VIIi, Theil, Kndaliosturus priscus Cred: Zertschrift der deutschen geologischen Gesellschaft, v 41,
oo 319 342
Ebe;th, D A, and Berman, D S , 1983, Sedimentology
and paleontologv of Lower Permian fluvial redbeds of
report: New
north-central New Mexico-nreliminarv
MericoGeology, v \, no 2, pp 21-25'
Kuhn-Schnyder, E ,1967, Das problem der Euryapsida:
Colloque Internationaux du Centre National de la Recherche Scientifique, no 153, pp 335-348
Langston, W , Jr , 1,953,Permian amphibians from New
Mexico: University of California, Publications in Geological Sciences, v 29, pp,349-476
Olson, E C, 1970, New and little known genera and
soecies of vertebrates from the Lower Permian of Oklahoma: Fieldiana.Ceology, v 18, pp 359-4J4
Peabody, F E , 1951,The origin of the astragalus of reptiles: Evoluiion, v 5, pp 339-344
-t
19521 Petrolacoscurus kansensis Lane, a Pennsyl-
vanian reptile from Kansas: University of Kansas Paleontological Confributions, Vertebrata, Art 1, 44 pp
Reisz, R R , 7977, Petrolacosarrus,the oldest known diapsid reptile: Science, v 196, pp 1,091.-1.,093
-r
1980, A protorothyridid captorhinomorph reptile
from the Lower Permian of Oklahoma: Royal Ontario
Museum, Life Sciences Contributions, no 121, pp 1
16
-,
1981, A diapsid reptile from the Pennsylvanian
of Kansas: Universi$ of Kansas, Museum of Natural
History Special Publications, no 7,74 pp
Reisz, R R, Berman, D S, and Scott, D, The anatomy
and relationships of the Lower Permian reptile Araeoscelis, in preparation
Rewcastle, S C, 1980, Form and function in lacertilian
contribution to the analknee and mesotarsal joint-a
ysis of sprawling locomotion: London, Journal of Zoology, v 191, pp 147-770
Romer, A S , 7956, The osteology of the reptiles: University of Chicago Press, 772 pp
-,
1966, Vertebrate paleontology, 3rd edition: University o{ Chicago Press, 458 pp
-,
7967, Early reptilian evolution re-viewed: EvoIution, v 21., pp 821-833
Simpson, L C,1,979, Upper Cearyan and Lower Leonardian terrestrial vertebrate faunas of Oklahoma:
Oklahoma Geology Notes, v 39, pp 3-79
Stovall, J W, Price, L I, and Romer, A S, 1966,The
postcranial skeleton of the giant Permian pelycosaur
Cotylorhynchusronerli; Museum of Comparative Zoology, Bulletin, v 135, pp 1-30
Vaughn, P P, 1955, The Permian reptrle Araeoscelis restudied: Museum of Comparaiive ZooIogy, Bulletin, v
1."13,pp 305-457
-,I970,
Alternation of neural spine height in certain
Early Permian tetrapods: Southern California Academy
of Sciences, Bulletin, v 50, pp 80-85
Williston, S W, 1910, New Permian reptile-rhachitomous vertebrae: Journal of Ceology, v 18, pp 585-600
-,
7913, An ancestral lizard from the Permian of
Texas: Science, v 38, pp 825-825
!
f{ewMerico
Mineral
Symposium
Call for papers
The 5th annual New Mexico Mineral Svmposium will be held at the New Mexico Instiiute of
Mining and Technologyin Socorro, New Mexico,
on November 10 and 11, 1984.Sponsorsof the
annual symposium are the New Mexico Bureau of
Mines and Mineral Resources,the Albuquerque
Gem and Mineral Club, the New Mexico TechMineralogical Sociery the New Mexico Museum of
Natural History, and the University of New Mexico, Department of Geology.
This year's symposium will again feature 30minute papers, a si.lentauction, and a dinner on
Saturday night. The sponsors encourage professionals and amateurs alike to submit papers on
any one of a variety of topics-new mineral occurrences within the State. the historv of New
Mexico'sclassicrnineral-collecting
areas,the geology of ore deposits, and interesting mineral occurrencesin adjacent states-to name a few.
Abstractsare due by August 15, 7984 Complete
papers should be submitted within 6 months after
for publication in a symposium vollfi::",urto"
General registration for the 1984symposium is
$10.00;registration for students and senior citizens (over age 60) is $5.00.To obtain registration
information or to submit an abstract,contact Robert M. North, New Mexico Bureau of Mines and
Mineral Resources,Socorro,NM 87801,(505)8355246.
Scepter quartz from Kingston, New Mexico; rhodochrosite from Silverton, Colorado; topaz
from the Thomas Mountains, Utah; and barite from Superior, Arizona, rePresent minerals
from the four-corners states. Artist: Teresa Mueller
New Mexico Geology May 1984
39