A tiny Triassic saurian from Connecticut and the early evolution of the diapsid feeding apparatus

Following the Permo–Triassic Extinction, large-bodied diapsid reptiles—with a body length >1 m—rapidly expanded their ecological roles. This diversification is reflected in enormous disparity in the development of the rostrum and adductor chamber. However, it is unclear how marked the diversity of the feeding apparatus was in contemporary small-bodied diapsids. Here we describe the remarkably small skull (2.5 cm long) of a saurian reptile, Colobops noviportensis, gen. et sp. nov., from the Triassic New Haven Arkose of Connecticut, USA. The taxon possesses an exceptionally reinforced snout and strikingly expanded supratemporal fossae for adductor musculature relative to any known Mesozoic or Recent diapsid of similar size. Our phylogenetic analyses support C. noviportensis as an early diverging pan-archosaur. Colobops noviportensis reveals extraordinary disparity of the feeding apparatus in small-bodied early Mesozoic diapsids, and a suite of morphologies, functionally related to a powerful bite, unknown in any small-bodied diapsid.

• This character was not ordered in 100 . As the states represent a transformational series with nested intermediates, we have ordered it here. 6) Premaxilla, posterodorsal process, maxilla contact: (0) simple, straight suture; (1) margin/knob on the posterior margin of the posterodorsal process of the premaxilla fits into notch in the anterior surface of the maxilla; (2) anterior lamina of maxilla laps laterally over posterodorsal process of premaxilla.
• Taxa coded as "1" for character 44 are coded as "-"for this character.
• Taxa coded as "1" for character 44 are coded as "-"for this character. 48) Palatine. lateral tooth row, dental morphology: (0) similar to other palatal teeth; (1) enlarged relative to all other palatal teeth, akin to marginal teeth in size and morphology.

59)
Exoccipital, contact with dorsal elements of occiput: (0) exoccipitals columnar throughout their dorsoventral height, forming transversely narrow contact with dorsal occiput elements; (1) exoccipitals exhibit dorsomedially inclined processes which do not meet in the midline; (2) exoccipitals meet dorsally over the foramen magnum excluding the supraoccipital from that opening. ORDERED.
• Taxa code as "1" for this character are coded as "-" for character 266.

94)
Marginal dentition, implantation: (0) teeth situated in shallow groove (as in pleurodonty, thecodonty); (1) teeth superficially attached to tooth bearing bones, with limited extension of pulp cavity into the bone teeth; (2) superficially attached to tooth bearing bones, with no extension of pulp cavity into the bone (= true acrodonty). ORDERED.
• This character was not ordered in 100 . As the states form a logical series with intermediates, we have ordered it for this analysis.
• NOVEL CHARACTER. In nearly all taxa integrated into this analysis, the nasal meets the dorsal margin of the maxilla along some portion of the anteroposterior length of the rostrum. In most diapsid reptiles, this contact is dorsoventrally short, occupying a small amount of the dorsoventral height of the supra-alveolar portion of the maxilla (e.g., the pan-archosaurs Prolacerta broomi, SAM-PK 10018, UCMP 37151; Batrachotomus kupferzellensis 57 ; the squamate Iguana iguana, YPM R 13952). State 0 is illustrated by a specimen in Prolacerta broomi that is missing the anterodorsal portion of its left maxilla in Fig. S12A. • In several diapsid lineages, the nasal has a proportionally taller lamina that fits against most or all of the supra-alveolar portion of the maxilla. This tall lamina is present in Sphenodon punctatus 97 , a number of rhynchosaurs (e.g., Mesosuchus browni, SAM-PK 6536; Teyumbaita sulcognathus 52 and Colobops noviportensis (YPM VPPU 18835). This condition is illustrated using CT slice data in Fig.  S11B and three-dimensional volume renderings in Fig. S12B. 312) Jugal, lateral surface, anteroposteriorly oriented shelf (i.e., anguli oris crest): (0) restricted to main body of bone, (1) extends at least to anterior tip of anterior process of bone.
• In both 42,105 , this character incorporates a state for taxa in which the lateral shelf (anguli oris crest) extends onto the lateral surface of the maxilla as well as the anterior process of the jugal. 313) Postfrontal, posteromedial corner: (0) anteroposteriorly or posterolaterally inclined, (1) posteromedially inclined, resulting in transverse tapering of posterior portion of frontal.
• We illustrate our interpretations of these states and our reconstruction of the position of the bar relative to the orbit in Colobops noviportensis in Fig. S13. 316) Quadrate, dorsalmost portion: (0) tapering dorsally, (1) dorsally expanded into prominent convexity (cephalic condyle sensu 107 ).
• The term "cephalic condyle" is most often applied to the dorsal convexity on the quadrates of lepidosauromorph reptiles 88,107,109 . We here consider the similar convexity present in a wide range of early pan-archosaurs (e.g., Prolacerta broomi, BP/1 5375; Mesosuchus browni, SAM-PK 6536; Azendohsaurus madagaskarensis, FMNH PR 2751) to be homologous, such that the term would be applicable to both lepidosauromorphs and archosauromorphs. 317) Ectopterygoid, posterior expansion of lateral process in contact with jugal: (0) absent; (1) present, with prominent posterior process extending posteriorly from primary axis of lateral process.
• NOVEL CHARACTER. • Equivalent to 49 . This character was not presented in the analysis of reference 100 but it is included here to account for variation seen in Tanystropheidae. 323) Metatarsal five, ratio of proximodistal length of contact with distal tarsal four to proximodistal length of distal process: (0) >1, (1) <1.
• In most diapsid reptiles, the length of the contact between the fourth distal tarsal and the fifth metatarsal is equivalent to or shorter than the proximodistal length of the main shaft of the bone distal to that contact. This is the case in Youngina capensis 21

Supplementary Note 4: Modifications to characters and codings from the matrix of Pritchard and Nesbitt (2017)
The following are codings changed from the dataset of ref 100 . Some are corrections from the original dataset, whereas others are revised based on firsthand studies of material that was not incorporated into ref 100 . Changes are only included for characters that were unchanged from the original study or changed only slightly (indicated in bold above).               Table 1. Measurements of the transverse widths of the post-orbital portion of the skull at the anteroposterior midpoint of the supratemporal fenestra, the transverse width of the supratemporal fossae (here measured from the supratemporal fossae) at the same point, and the anteroposterior length of the skull from the anterior tip of the preserved rostrum to the posterior margin of the parietal. Measurements from fossil taxa were derived from the literature or from photographs by A. Pritchard. Measurement methods can be found in Appendix D.