Lessons learned about the base of the Reptilia – part 2

Yesterday we looked at pertinent traits 1-39 from the large reptile tree that had a character distribution and division at the base of the reptilia.  Today we’ll continue with traits 40-128, finishing up the cranial traits.

45. Frontal with posterior processes – new Archosauromorpha.

46. Intertemporal absent (actually fused to the parietal making it that much wider) – the Reptilia

48. Postparietals (and tabulars and supratemporals) angled dorsally – the Reptilia

52. 69. Squamosal descent angle is a big curve, the so-called otic notch, in pre-reptiles. It  is obtuse and not indented in reptilia (but reversed following Romeria primus).

53. Postorbital/parietal contact (remember #46 the intertemporal becomes fused to the parietal making this possible) – the Reptilia

56. Postorbital appears as a strip beneath an overlapping postfrontal in Gephyrostegus to new Lepidosauromorpha. The postorbital is otherwise triangular.

57. Frontal/nasal angle is > 45 degrees from the midline in pre-reptiles and the new Lepidosauromorpha. The angle forms a zig-zag in the new Archosauromorpha.

58. Frontal proportions are not less than 4:1 in pre-reptiles and the new Archosauromorpha. The proportions are less than 4:1 in the new Lepidosauromorpha but not Cephalerpeton.

64. The squamosal descends to mid-level, due to a posteriorly deep quadratojugal in pre-reptiles and the new Lepidosauromorpha. The squamosal extends to the ventral rim in the new Archosauromorpha.

73. The quadrate leans anteriorly in pre-reptiles and the new Archosauromorpha, but this short bone is vertical in the new Lepidosauromorpha.

79. The opisthotic rises in pre-reptiles, but is lateral with posterior fenestra in reptiles.

82. The supratemporal is long, not large in reptiles, but this reverses in the new Lepidosauromorpha after Romeria primus.

94. The suborbital fenestra is present in the new Lepidosauromorpha, but not in  Cephalerpeton.

96. The vomer teeth are small, not fang-like in the Reptilia.

102. Pterygoid extends anterior to the palatines – restricted to Brouffia and Captorhinidae, but this character is largely unknown in basal reptiles due to various taphonomic circumstances

105. Pterygoid triangular – Gephyrostegus + Reptilia

108. Premaxilla tooth number – Gephyrostegus and Brouffia have 4. Cephalerpeton to the concordians have less than 4. All others have more than 4.

109. Medial premaxillary tooth longer than the others – the new Lepidosauromorpha

113. Canine maxillary teeth – Captorhinidae + several new Lepidosauromorpha and paleothyrids in the new Archosauromorpha by convergence

119. Mandible tip – rises in Cephalerpeton to Concordia, descends in Captorhinidae and is straight in all others

128. Mandible shape ventrally – straight anteriorly then convex posteriorly in pre-reptiles to Brouffia. Straight in Westlothiana and derived taxa. Convex in the new Lepidosauromorpha.

Post-crania tomorrow.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.