Azendohsauridae

Nesbitt, Sterling J., Flynn, John J., Pritchard, Adam C., Parrish, J. Michael, Ranivoharimanana, Lovasoa & Wyss, André R., 2015, Postcranial Osteology Of Azendohsaurus Madagaskarensis (? Middle To Upper Triassic, Isalo Group, Madagascar) And Its Systematic Position Among Stem Archosaur Reptiles, Bulletin of the American Museum of Natural History 2015 (398), pp. 1-126 : 86-87

Azendohsauridae + Trilophosauridae

(Bremer 5 1)

SUPPORT: Unambiguous synapomorphies include: prominent postglenoid process on coracoid, terminating in thickened margin (148-1*); entire anterior margin of scapula markedly concave (219-1*); constricted scapula blade, the anteroposterior length of the constriction less than one-quarter the proximodistal length of the scapula (220-1*); ventral tubercle of the pedal (or manual) ungual well developed and extended ventral to the articular portion (233-1*); anteroventrally deflected anterior end of the dentary (241-1*); atlas centrum fused to axial intercentrum (243-1*).

Other possible synapomorphies: AC- CTRAN: Parabasisphenoid, orientation more vertical (208-1). DELTRAN: Medial process of the postorbital situated deep to the postfrontal (27-0); supratemporals absent (36-0); tympanic crest of the quadrate absent (43-0); one field of dentition on the anterior process of the pterygoid (49-0); exoccipitals and opisthotic fused (62-1); paroccipital contribution of the prootic contributes laterally tapering lamina to the anterior surface of the paroccipital process (75-1); medial centrale of manus present (158-1); lateral and medial sides of the distal pedal phalanges converging anteriorly (234-1); gastralia small in number (5 well separated) (238-1).

DISCUSSION: Within Allokotosauria, Trilophosauridae and Azendohsauridae form a pairing. This relationship, despite being poorly supported by decay indices, is supported by a number of unambiguous character states that can be scored in the nearest outgroup, Pamelaria dolichotrachela . For example, A. madagaskarensis and Trilophosaurus share a very long postglenoid process of the coracoid (148-1), a feature clearly absent in Pamelaria dolichotrachela (fig. 72). The scapulae of A. madagaskarensis and Trilophosaurus are tall relative to their widths and have highly constricted shafts, whereas the scapula of P. dolichotrachela (Sen, 2003) is proportionally shorter and more similar to that of the outgroup taxon Prolacerta broomi (BP/1/2675). The atlas centrum is fused to the axial intercentrum in A. madagaskarensis and Trilophosaurus , but is clearly separate in P. dolichotrachela (Sen, 2003) . Azendohsaurus madagaskarensis and Trilophosaurus share large unguals with prominent ventral tubercles, whereas the ungual tubercle of P. dolichotrachela (Sen, 2003) is small. Azendohsaurus , Trilophosaurus , and Teraterpeton hrynewichorum share an anteroventrally deflected anterior end of the dentary, whereas the anterior portion of the dentary of P. dolichotrachela (Sen, 2003) is horizontal. Lastly, the presence of epipophyses on the cervical postzygapophyses of A. madagaskarensis and Trilophosaurus , and the plesiomorphic absence of epipophyses in P. dolichotrachela , also unites Azendohsauridae + Trilophosauridae to the exclusion of P. dolichotrachela , even though this is not a character state optimized outside Azendohsauridae + Trilophosauridae because of a complex distribution as a result of homoplasy and missing data.

Although Pamelaria dolichotrachela is identified as the nearest outgroup of Trilophosauridae + Azendohsauridae , curiously a number of derived character states occur in Azendohsauridae and Pamelaria dolichotrachela to the exclusion of trilophosaurids, apparently homoplastically (see below).

Azendohsauridae 5 Azendohsaurus (currently A. madagaskarensis + A. laaroussi i) (Bremer 5 2)

SUPPORT: Unambiguous synapomorphies include: prominent anteroposteriorly orient- ed ridge present on the medial surface of the maxilla (201-1*); dorsal apex of the maxilla is a separate, distinct process having a posteriorly concave margin (202-1*); crown height of the upper dentition is lower than that of the lower dentition (211-1*).

Other possible synapomorphies: AC- CTRAN: Nasal oriented parasagitally at contact with prefrontal (9-0); pineal foramen present (22-0); posterior process of the postorbital contributes to more than onehalf the length of the supratemporal bar (28-1); anteroposteriorly slender descending process of the squamosal (34-1); posterior margin of quadrate straight and vertical (41-0); internal carotids appear not to enter braincase (67-2); basipterygoid processes of the parabasisphenoid oriented anterolaterally (70-0); laterosphenoid ossification present but fails to reach the ventral surface of frontals (72-1); retroarticular process absent (86-1); ribs fused on the posteriormost trunk vertebra (124-1); neural spines of the trunk vertebrae long and low, lesser in dorsoventral height than anteroposterior length (129-1); chevrons broaden distally, forming subcircular expansion (136-3); proximal end of head of the femur well ossified and convex (178-0); internal trochanteric crest of the femur does not reach proximal surface of femoral head (179-0); pedal centrale absent as distinct ossification, fused to astragalus (184-0); ventrolateral margin of the lateral process of the calcaneum “curls” externally (190-1); transverse width of the distal end of the humerus equal to or greater than 2.5 times the minimum width of the shaft (221-1). DEL- TRAN: Anterodorsal process (5 nasal process) of the premaxilla absent, creating a confluent external naris (3-1); marginal dentition serrated (90-1); Interdental plates present in the marginal dentition (96-1).

DISCUSSION: The two members of Azendohsauridae , Azendohsaurus madagaskarensis and A. laaroussii , are obviously closely related. Both taxa share a prominent anteroposteriorly oriented ridge on the medial surface of the maxilla, a “pseudoantorbital fenestra” where the dorsal apex of the maxilla forms a separate, distinct process with a posteriorly concave margin, and a distinct difference in crown height between the upper and lower dentitions as well as other characters noted as unambiguous or ambiguous synapomorphies (fig. 7). These taxa likely share many additional character states exclusive of those that are present in other archosauromorphs, but A. laaroussii is currently described on the basis of only a few elements (e.g., teeth, maxilla, dentary) even though postcrania are preserved and under study by other investigators (Jalil and Knoll, 2002).

Our phylogenetic analysis identified Pamelaria dolichotrachela as the nearest outgroup of Azendohsauridae + Trilophosauridae , based on numerous character states (see above). Even so, a number of character states shared by P. dolichotrachela and A. madagaskarensis to the exclusion of Trilophosauridae emerged during construction of our data matrix. For example, P. dolichotrachela (Sen, 2003) and A. madagaskarensis lack an anterodorsal process (5 nasal process) of the premaxilla (3-1). This character state is also present in rhynchosaurs, but the premaxillae of P. dolichotrachela (Sen, 2003) and A. madagaskarensis are nevertheless very similar in this respect. Furthermore, the marginal teeth of P. dolichotrachela (Sen, 2003) and A. madagaskarensis are serrated (90-1). Additionally, P. dolichotrachela (Sen, 2003) and A. madagaskarensis share a deep depression on the ventral surface of the basicranium that is restricted to the parabasisphenoid (68-2). Whereas serrated teeth and a deep depression on the ventral surface of the parabasisphenoid occur among some Archosauriformes , they occur infrequently outside that clade among archosauromorphs. The cervical vertebrae of P. dolichotrachela and A. madagaskarensis are similar in their dorsoventrally short neural spines and strong transverse waisting of the centra. Comparison of P. dolichotrachela and A. madagaskarensis is hampered, however, by our inability to score many skull characters for P. dolichotrachela , owing to poor preservation and high fracturing of the bone surfaces. To investigate this pairing further, we built a constraint tree in PAUP with P. dolichotrachela and Azendohsaurus as sister taxa and ran the analysis using the same methodology as stated above. As a result, the relationships of Allokotosauria remained the same, although some support values changed at the base of the clade and at Trilophosauridae . The constrained analysis added only two more steps over the original analysis, thus indicating that the phylogenetic position of P. dolichotrachela is poorly supported within Allokotosauria. Nonetheless, irrespective of which placement of P. dolichotrachela ultimately is most strongly supported, homoplasy of many craniodental features within Allokotosauria is unavoidable.