DIAPSIDA Osborn 1903
Gauthier, Kluge, and Rowe 1988a
Long and Murry 1995
Long and Murry, 1995, by monotypy.
Long and Murry, 1995
? 1989 "
Acallosuchus rectori" in part;
Murry and Long, p. 32.
? 1989 proterochampsid gen. et sp. nov;
Murry and Long, p. 48.
Long and Murry, p. 195, figs. 197, 198.
Hunt, Heckert, Lucas and Downs, p. 269, fig. 2.
Vancleavea campi; Parker, p. 43.
Vancleavea campi; Irmis, p. 71, figs.4j, k.
sp.; Parker and Irmis, p. 48, figs. 3d, e.
Hunt, Lucas and Spielmann, p. 59, figs. 2, 3, 4.
PEFO 2427, fragmentary postcranial skeleton.
Referred Specimens from Petrified Forest National Park.
PEFO 31202, left femur, from locality PFV 215 (Zuni Well Mound), Petrified Forest Member. PEFO 33978, partial skeleton, from locality PFV 231 (The Giving Site), Petrified Forest Member. PEFO 34035, partial skeleton, from locality PFV 215 (Zuni Well Mound), Petrified Forest Member. PEFO 34224, distal end of femur, and PEFO 34231, sacral centrum, both from an unknown locality in the Blue Mesa Member. UCMP 178050, caudal vertebra, from UCMP locality V82251 (PFV 97 - Saurian Valley), Sonsela Member. Locality information for these specimens is available at Petrified Forest National Park for qualified researchers. See
Hunt et al. (2002) for further referred specimens outside Petrified Forest National Park.
Non-archosaurian archosauriform distinguished by the following autapomorphies: 1) cervical centra with a length/width ratio of greater than 1.5; 2) mid-cervical centra with a convex posterior articular face; 3) dorsal vertebral centra with weakly developed double ventral keels; 4) caudal centra that are subrectangular in ventral view with almost no waisting and possessing extremely well-developed sharp ventral keels; 5) a carapace of numerous subrounded osteoderms, each possessing a pronounced median keel and anterior projection; and 6) ilium with a tall anteriorly directed blade that does not extend anterior to the pubic peduncle, which superficially resembles the ilium of drepanosaurs. Distinguishing synapomorphies include 1) loss of the "terminal" femoral head and ventral ridge system (
Carroll 1988) as in basal archosauromorphs and basal archosauriforms; 2) cervical vertebral diapophyses and dorsal vertebral parapophyses divided by the neurocentral suture as in
Erythrosuchus; and 3) presence of a prominent, medially directed femoral head as in
Chanaresuchus, and archosaurs.
Blue Mesa, Sonsela, and Petrified Forest Members, Chinle Formation, Arizona; Siltstone Member, Chinle Formation, New Mexico; Los Esteros Member, Santa Rosa Formation, Dockum Group, New Mexico; Bull Canyon Formation, Dockum Group, New Mexico; Redonda Formation, Dockum Group, New Mexico; and Tecovas Formation, Dockum Group, Texas (Long and Murry 1995;
Hunt et al. 2002).
Late Triassic, Norian (Muttoni et al. 2004;
Furin et al. 2006;
Much of the left dentary is preserved in PEFO 33978 (Figure 3). This bone is mediolaterally slender and dorsoventrally deep with a dorsally expanded anterior end. The alveoli are badly preserved but it appears that the entire length of the dentary possessed teeth with a thecodont tooth implantation. The ventrolateral surface of the anterior portion of the dentary has a pattern of thin, elongate grooves which terminate anteriorly as small foramina. The medial surface is excavated by a prominent
meckelian groove (Figure 3.2). The total length of the lower jaw, based on the preserved dentary length (approximately 77 mm), is greater than the length of the femur (based on comparison with PEFO 31202, which represents an individual similar in size to PEFO 33978). At its deepest point, at the dorsal expansion of the anterior end, the dentary is 31 mm high. As figured by
Wu and Russell (2001, figure 2) the anterior portion of the dentary in
is also dorsoventrally expanded but not to the degree seen in PEFO 33978.
PEFO 33978 preserves two
articulated cervical vertebrae (Figure 4.1) and two isolated centra (Figures 4.2-4.3). The mediolaterally compressed centra are elongate (L/H ratio of 2:1) and 40 mm in length. The posterior articular face is flat, whereas the anterior articular
face is concave. The parapophysis is represented by an expansion along the edge of the anterolateral surface of the centrum (Figure 4.1). The ventral surface is strongly keeled (Figures 4.1-4.2). The diapophysis is divided by the neurocentral suture, between the anterior portion of the centrum and the neural arch. The neurocentral sutures appear to be articulated but open (Brochu 1996;
Irmis 2007). The prezygopophyses are elongate, inclined medially approximately 45 degrees and fit into a shallow concavity at the base of the postzygopophyses of the proceeding vertebra (Figure 4.1). The postzygopophyses project posteriorly past the posterior face of the centrum and strongly overlap the neural arch of the subsequent vertebra. The neural spine is tall (25 mm) and elongate (20 mm); rectangular in lateral view (Figure 4.2). The apex of the spine is not mediolaterally expanded into a "spine-table." The cervical vertebrae lack post-axial intercentra.
An isolated, well-preserved cervical centrum from PEFO 34035 (Figures 4.4-4.7) differs from the vertebrae described above in possessing well-developed parapophyses (Figures 4.4-4.5). The anteroventral surface of the centrum is slightly beveled (Figure 4.7) and the dorsal surface is broad, forming a shelf (the ventral portion of the diapophysis) where it meets the ventral surface of the neural arch (Figure 4.6). The lateral surfaces of the centrum are concave, and the ventral surface possesses a sharp anteroposteriorly directed keel (Figure 4.5).
One complete dorsal vertebra and four isolated centra are preserved in PEFO 33978. The centra are blocky, elongate (L/H ratio of 1.5:1), and platycoelus. The centra are similar size with an average length of 35 mm. The articular faces are tall and oval. The ventral surface of the centrum is broad and flat, with two very weakly developed keels that are only faintly visible (Figure 5). The dorsolateral surface of the centrum flares laterally at the neurocentral suture. The parapophysis consists of a pronounced, slightly anterolaterally projecting knob (Figures 4.8-4.9) located on the anterolateral corner of the centrum and at the base of the neural arch. The neurocentral suture divides the parapophysis with only a small percentage of the articular facet located on the neural arch (Figure 4.10). None of the neurocentral sutures in PEFO 33978 are closed.
The neural arch of the dorsal vertebra (Figures 4.11-4.12) is tall (27 mm), roughly equal to the height of the centrum. The prezygopophyses project anterodorsally just past the anterior articular face of the centrum. The articular facets of the prezygopophyses are angled about 45 degrees medially, similar to the cervical series; however, the postzygopophyses do not project as far dorsally as those of the cervical series.
The short (18 mm) transverse processes are anterolaterally expanded, project posterolaterally, and are situated posteriorly on the neural arch
Figures 4.11-4.12). The articular surface (divided diapophysis) is broad. Distinct parapophyses and diapophyses in the cervical and dorsal vertebrae demonstrate that the cervical and dorsal ribs of
Long and Murry (1995) two sacral centra are preserved in the holotype (PEFO 2427); sacral centra are also known from PEFO 34035 and PEFO 34231.
These centra are longer than high (L/H ratio of 1.9:1 with lengths of 30 mm and 35 mm), platycoelus, and strongly keeled ventrally (Figures 4.13-4.16). In PEFO 2427 (Figure 4.16), there is a double keel (Long and Murry 1995), whereas in the larger specimens PEFO 34035 (35 mm length;
Figure 4.13) and PEFO 34231 (36 mm length) there is only a single keel. The significance of this difference cannot be unambiguously determined given the material at hand, but either the two keels merge into a single larger keel through ontogeny of the individual or sacrals one and two differ in the number of keels that they possess. Other possibilities include individual or taxonomic differences.
Raised facets for attachment of the sacral ribs cover much of the lateral side of the centrum (Figures 4.13-4.16). In one centrum (PEFO 2427) and the preserved sacral in PEFO 34035, the facet is subrounded in lateral view (Figure 4.15), whereas in PEFO 34231 and the other centrum in PEFO 2427 the facet is more anteroposteriorly elongate and particularly pronounced anteriorly.
Long and Murry (1995) considered the centra with the subrounded facet from PEFO 2427 to represent the second sacral. All preserved sacral centra have open neurocentral sutures and no neural arches from this region are preserved.
It is possible that the smaller centrum, figured by
Long and Murry (1995, figure k) as the first sacral, represents an anterior caudal vertebra instead and that chevrons did not occur in the anteriormost caudals, similar to other archosauriforms. Evidence for this interpretation includes a shorter centrum (30 mm length) and the lack of a broad rib attachment; however, this
interpretation cannot be confirmed with the evidence at hand.
Hunt et al. (2005) also considered this centrum
to belong to the caudal series.
Long and Murry (1995) mention a centrum in PEFO 2427 that could represent an anterior caudal because of the lack of chevron facets but did not provide a more explicit identification of the element.
The caudal vertebrae of
(Figures 4.17-4.18) are distinctive
because of their box-like, rectangular shape in ventral view with almost no waisting and by the presence of two sharp ventral keels that originate at the posterior margins of the chevron facets and delineate the ventral surface of the centrum
(Long and Murry 1995).
All of the preserved caudal vertebrae are longer than high with oval articular faces with well- developed rims. In PEFO 2427 the presumably more anterior centra, which are anteroposteriorly shorter (average of 30 mm in length), have anteroposteriorly elongate, laterally projecting transverse processes. The more elongate (> 30 mm in length), and presumably more posteriorly
situated caudal centra completely lack transverse processes.
A fragment from PEFO 34035 (Fig. 6) represents the distal portion of the right scapula. Although the morphology of this fragment also appears consistent with the proximal portion of the coracoid, we interpret it as belonging to the scapula because of the lack of a noticeable coracoid foramen. A rugose articular surface for the coracoid demonstrates that the scapula and coracoid were separate elements and were not co-ossified, at least for the preserved ontogentic stage of the specimen. From the broken cross-section it appears that the scapular blade was very thin mediolaterally. A small shallow notch is present just dorsal to the glenoid.
Both ilia are preserved in PEFO 34035. The left ilium is missing the posterior-most portion of the iliac blade and is diagenetically fused to the left femur; however, the right ilium is isolated and complete (Figure 7.1). The iliac blade is tall (40 mm) and separated from the acetabular by a well-defined neck. The blade apex is formed by the anterior portion of the blade. The dorsal margin slopes posteriorly toward a small posterior process.
Neither the anterior or posterior portions project past the pubic or ischiadic peduncles; thus, the blade is extremely anteroposteriorly narrow. The mediodorsal surface of the iliac blade possesses elongate
striations, which originate at the neck and progress anterodorsally to the blade apex, representing attachment areas for the sacral ribs (Figure 7.2). The tall iliac blade differs greatly from those of
(Ewer 1965, figure 11), and
(Wu and Russell 2001, figure 9) which are low with a nearly horizontal dorsal margin and is more similar to those of non-archosauriform archosauromorphs. Particularly striking is the strong similarity of the ilium of
with that of
(Renesto 1994, figures 11-12).
also has a tall, expanded iliac blade; however, it differs from
in its strong lateral expansion (Weems 1980, figure 21, pl. 7).
The ilium makes up almost the entire acetabulum. A distinct supra-acetabular rim is present, and the anterior margin of the ilium is almost twice the length of the posterior margin. The pubic and ischiadic peduncles meet at an obtuse angle; both are crescentic in distal view, curving slightly laterally (Figure 7.3;
Hunt et al. 2005). The pubic peduncle is mediolaterally thickened compared to the ischiadic peduncle.
The proximal portions of both pubes are preserved in the holotype material (PEFO 2427). The pubis only contributes slightly to the acetabulum and possesses a distinct posterodorsal process (Figure 7.4). The articular surface for the ilium is mediolaterally thickened, rugose, and crescent shaped (Long and Murry 1995;
Hunt et al. 2005). This surface continues posteriorly onto the posterior process and is confluent with a second rugose articular surface that is vertical and faces posteriorly to meet an anterior edge of the proximal portion of the ischium. The ventral surface of the posterior process of the pubis forms the dorsal rim of the obturator foramen. Because the ventral portion of the pubis is missing, it is not clear whether this foramen was fully enclosed by the pubis, or if it bordered the symphysis with the ischium
(Long and Murry 1995). It is possible that the pubis and ischium met below this foramen, similar to basal archosauromorphs. The presence of a distinct thyroid fenestra, suggested for the Ghost Ranch specimen (Small and Downs 2002), cannot be determined from the PEFO material.
The ischium is known from proximal portions of both ischia preserved in PEFO 2427 and the proximal portion of the left ischium in PEFO 34035. Approximately a quarter of the acetabulum is formed by the ischium, a larger contribution than that of the pubis, but much less so than that of the ilium. The acetabular
portion forms a distinct ventrally flaring semicircular rim (Figure
7.4; Long and Murry 1995). The articular surface for the ilium is rugose and curves posteromedially. There is an anterior projection with a subrounded anteriorly facing articular
facet for the pubis. The ventral portion is not preserved. The groove mentioned
by Long and Murry
(1995) and questioned by
Hunt et al.
(2005) is interpreted here as a scallop-shaped fracture of the bone surface.
Humeri are preserved in PEFO 2427 (left, Figures 8.1-8.3), PEFO 33978 (proximal ends of the left and right, distal end of the left?, not figured), and PEFO 34035 (left, minus the distal end,
Figures 8.4-8.5). The humerus has a distinct yet weakly developed deltopectoral crest as well as a distinct internal tuberosity (Figures 8.3-8.5). Because none of the elements are complete, the offset between the proximal and distal ends cannot be determined. The proximal articular surface is convex in ventral view and roughly oval in proximal view. Along this surface the humerus thickens medially, forming the medial tuberosity, which is triangular in PEFO 2427 (Figure 8.3) and PEFO 33978, but gently rounded in PEFO 34035 (Figures 8.4-8.5). The ventrolaterally directed deltopectoral crest is best preserved in PEFO 34035 and is restricted to the dorsoventral surface. The deltopectoral crest does not extend ventrally along the shaft (Figure 8.5). The overall morphology of the humerus is very similar to that of
(Wu and Russell 2001, p. 44), where the deltopectoral crest is not well-developed and "is more appropriately regarded as a continuation of the" proximal head.
Wu and Russell (2001) also note the presence of this humeral morphology in
The distal end of the humerus is best preserved in PEFO 2427. The ento- and ectocondyles are distinct; the entocondyle is larger than the ectocondyle
(Long and Murry 1995). There is a very slight concavity between the two condyles (contra
Long and Murry 1995) and the distal surface is expanded medially forming a distinct entepicondyle (Figure 8.1). No entepicondylar or ectepicondylar grooves or foramina are present. The proximal and distal ends of the humerus are of equal width. The best preserved humerus (PEFO 34035) has a length of approximately 100 mm.
The proximal end of the left ulna is present in PEFO 34035 (Figure 8.6). The proximal articular surface is gently rounded convexly, and the head is inclined slightly posteriorly. The sigmoid notch is weakly expressed. An olecranon process is present but not strongly developed.
The femur is fairly derived in its morphology in comparison with that of basal archosauromorphs in that the head is slightly offset with a distinct neck and not "terminal" (sensu
Carroll 1988). The enlarged intertrochanteric fossa and ventral ridge system found in basal amniotes, including basal archosauromorphs (Carroll 1988), are not present. The proximal articular surface is oval in proximal view and lacks a medial tuberosity. In PEFO 2427 there is a low, elongate, rugose ridge where the head meets the shaft (Figure 9.1) which
Long and Murry (1995) and
Hunt et al. (2005) considered to represent the 4th
trochanter; however, this ridge is not present in PEFO 34035, although it is possible that this muscle attachment surface did not ossify in this specimen. The femur of
is much more similar to that of
(SAM-PK-5867), Turfanosuchus (Wu and Russell 2001, figure 10), and
(USNM 186989) with its sigmidal curvature, "paddle-shaped" proximal end, and weakly developed distal condyles (Figures 9.2-9.5), than the femora of
, which are straighter and expanded proximally with a prominent intertrochanteric fossa (Cruickshank 1972;
Gower 2003). However, it differs from
and pseudosuchians in lacking a distinct posterior medial tuberosity and a prominent fourth trochanter (Wu and Russell 2001, figure 10;
Nesbitt 2007). On the right femur of PEFO 34035 there is a pronounced posterior 'kink' just ventral to mid-shaft (Figures 9.4-9.5) that is only weakly developed on the left femur from the same individual. A distinct ridge is present between this 'kink' and the medial distal condyle (Figure 9.4). There is a weakly developed intercondylar fossa between the distal condyles (Figure 9.2). The identity of the small fragment that
Long and Murry (1995) took to be part of the distal end of the femur in PEFO 2427 is confirmed by the new material (see discussion in
Hunt et al. 2005). Complete femora from PEFO 34035 have lengths of 128 mm.
Proximal portions of tibiae are preserved in both PEFO 34035 and PEFO 2427 (Figure 9.6-9.11). In proximal view the element narrows anteriorly forming a distinct, but weak, cnemial crest (Figure 9.6-9.7).
The lateral margin is straight, the medial margin slightly concave.
Long and Murry (1995) and
Hunt et al. (2005) identified the tibial fragment from PEFO 2427 as from the right side (Figure 9.6); however, based on the lateral curvature of the anterior tip of the cnemial crest (despite the slight breakage), this element is probably from the left side. Nonetheless, both sets of authors also interpreted the element backward and thus the 'posterolateral' ridge described by those authors is actually oriented anteromedially (Figure 9.8). Furthermore, PEFO 34035 demonstrates that this ridge terminates ventrally where the proximal portion of the tibia narrows to form the main shaft (Figure 9.9).
Numerous osteoderms are preserved in the Petrified Forest Member material; however, most of these are poorly preserved. The osteoderms are sub-rounded with a median keel, prominent anterior prong, and serrated margins and are best preserved in PEFO 33978 (Figures 10.1-10.2). Unfortunately, the osteoderms are poorly preserved in the holotype; however, the fragmentary keeled osteoderms ("ankylosaur"
type of Long and Murry 1995)
are diagnostic of the genus (Hunt
et al. 2002).
Long and Murry (1995) also described two additional osteoderm morphotypes, tall, triangular osteoderms, and conical osteoderms, both described as "
-like." Neither of these morphotypes can be identified in PEFO 33978 or PEFO 34035.
Hunt et al. (2005) considered the conical osteoderms to belong to the diminutive aetosaur
, although there is no direct evidence for this interpretation.