Fig. 8. The left mandible and associated quadrate of Conophis lineatus concolor (UMMZ S-788) showing (A) lateral and (B) medial views. × 3. Teeth shown by means of broken lines were represented only by their sockets.
Mandible.—The dentary ([fig. 8]) is compressed laterally and rounded below. The teeth, which are longest about one-third of the way from the anterior end of the dentary, are set in sockets on the medial side of the bone. The posterior half of the dentary overlies the fused surangular-prearticular part of the articular. Ventrally, the posterior part of the dentary underlies the splenial, which is set in a median trench within the dentary. Near the common suture of the dentary and the splenial is the large inferior alveolar foramen; completely within the splenial and ventral to the inferior alveolar foramen is the anterior mylohyoid foramen. Posterior to the splenial and also forming a part of the ventral surface of the mandible is the wedge-shaped angular, which lies directly beneath the fused surangular-prearticular. As has been implied, the articular, the surangular, and the prearticular are fused. The prearticular part of this bone forms a part of Meckel's canal. In the surangular part, immediately posterior to the end of the dentary, is the large surangular foramen. Lying in a longitudinal axis along the medial surface of the articular is a high crest, dorsal to which is a deep hollow. The lateral wall of the articular above this hollow is thin and rounded dorsally; the ventral surface is uniformly round and slightly curved dorsally, except that it ends with a short tympanic crest, which projects beyond the articulation with the quadrate. Where the quadrate articulates with the dorsolateral surface of the posterior portion of the squamosal, the former is broad and has a high mid-lateral crest, which extends about one-third of the distance down the quadrate before disappearing. The columellar process (the place of fusion of the columella) is about two-thirds of the way down the medial surface of the quadrate. Ventrally the quadrate has a narrow neck dorsal to its articulation with the articular. The articulation is formed by two lateral flanges of the quadrate that fit over a medial ridge formed by the articular.
Teeth on the maxillary and pterygoid decrease in size posteriorly, whereas those of the dentary do likewise except for the first one or two that are usually slightly smaller than those immediately posterior. The palatine teeth are subequal in size. The enlarged, grooved teeth on the maxillary are in shallow sockets on the posteroventral surface of the posterior knob of the maxillary. These teeth point posteriorly. The grooves are deep and are situated anterolaterally. One or two enlarged grooved teeth are present on a given maxillary. There seems to be a correlation between the type of preservation, the age of the snake, and the number of grooved teeth. Old (large) individuals always have only one grooved tooth that is rooted and functional, whereas some of the younger animals have two in place. Usually replacement teeth are present in alcoholic specimens, but these unrooted teeth are lost in the preparation of dried skeletons. Thus, it seems that in Conophis only one pair of grooved teeth is functional at any one time, although usually replacement teeth are present behind and beside the functional one. Some specimens have one tooth in the medial socket on one side and one in the lateral socket on the other. Replacement teeth on the maxillary and dentary are present in the buccal tissue on the medial side of the bones, whereas on the palatines and pterygoids, the replacement teeth are present laterally. Apparently there are no significant differences in dentition among the members of the genus Conophis.
The fiftieth vertebra of Conophis vittatus (UMMZ 82642) can be described as follows: The neural spine is elongate, thin and low; the posterior edge is sharply emarginate, and the anterior edge is only slightly emarginate. The zygosphene is thin dorsoventrally; in a ventral or dorsal view the zygosphene has a slightly concave anterior edge, the flat surface of which is oriented ventrolaterally. The centrum is elongate and triangular from below; it is widest at the paradiapophyses and narrowest at the short condylar neck. The condylus is directed posteriorly. The centrum, when viewed laterally, is slightly concave and has prominent subcentral ridges that extend from the median side of the paradiapophysial articular surfaces posteriorly to the neck of the condylus. The paradiapophysial articular surfaces are well developed and have two facets. The diapophysial surface is larger and more spherical than the parapophysial one. The parapophysial process projects beyond the parapophysial articular surface and is nearly even with the lip of the cotyle, which is slightly oval. The neural arch is slightly depressed; its width is somewhat less than the width of the cotyle. The articular surfaces of the postzygapophyses are oval and are directed posterolaterally. There is a strongly developed concave interzygapophysial ridge. A well-developed accessory spine extends laterally beyond the oval articular facets of the pre-zygapophysis and forms a slightly flattened, blunt spine. Excellent drawings of the middle thoracic vertebra of Conophis lineatus dunni from Honduras were published by Auffenberg (1958:6).
The hemipenes of Conophis are moderately caliculate, having spines covering the surface from the base to near the apex ([fig. 9]). These spines are largest near the base and are reduced to small papillate projections near the apex. The apex terminates in a small disc having three to five laminae in C. vittatus and one lamina in C. lineatus concolor. The sulcus is bifurcate; the fork is near the base and almost gives the appearance of two sulci on some specimens. Distally the apices are widely separated, and the intervening space gives the hemipenis a slightly bilobed appearance in some species (especially C. vittatus) or a deeply bilobed appearance in others (especially C. lineatus concolor).