Part 4

_Tomodon vittatus_, Bocourt, Journ. de Zool., p. 407, 1876.

_Conophis sumichrasti sumichrasti_ Cope, Journ. Acad. Nat. Sci. Philadelphia, ser. 2, 8:137, 1876 (Types.--United States National Museum, nos. 29123, 30258; type locality.--Tehuantepec, Mexico); Bull. U. S. Natl. Mus., 32:77, 1887; Smith and Taylor, Univ. Kansas Sci. Bull., 33(pt. 2):334, March 20, 1950; Maldonado-Koerdell, Inst. Mexicanos Recursos Nat. Renov., p. 124, 1953.

_Conophis sumichrasti viduus_ Cope, Journ. Acad. Nat. Sci., Philadelphia, ser. 2, 8:137, 1876 (Type.--United States National Museum, no. 30259; type locality.--Tehuantepec, Mexico); Bull. U. S. Natl. Mus., 32:77, 1887; Cochran, Bull. U. S. Natl. Mus., 220:167, 1961.

_Conophis sumichrasti_, Cope, Proc. Amer. Philos. Soc., 18:271, August 11, 1879; Sumichrast, Bull. Soc. Zool. France, p. 182, 1880; Cope, Trans. Amer. Philos. Soc., 18:194, April 15, 1895; Cochran, Bull. U. S. Natl. Mus., 220:167, 1961.

_Tachymenis lineata_ (in part), Garman, Mem. Mus. Comp. Zool., 8:60-61, July, 1884.

_Conophis vittatus sumichrasti_, Cope, Ann. Rept. U. S. Natl. Mus. for 1898, p. 1095, 1900.

_Conophis vittatus videns_ Cope, Ann. Rept. U. S. Natl. Mus., for 1898, p. 1095, 1900 (apparent _lapus_ for _viduus_).

_Conophis vittatus vittatus_, Cope, Ann. Rept. U. S. Natl. Mus. for 1898, p. 1095, 1900; Smith, Journ. Washington Acad. Sci., 31:119-120, March 15, 1941; Proc. U. S. Natl. Mus., 92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:408, October 29, 1943; Ann. Carnegie Mus., 30:91, November 2, 1944; Smith and Taylor, Bull. U. S. Natl. Mus., 187:44, October 5, 1945; Smith, Rev. Soc. Mexicanos Hist. Nat., 7:71, December, 1946; Smith and Taylor, Univ. Kansas Sci. Bull., 33(pt. 2):331, March 20, 1950; Davis and Smith, Herpetologica, 8:134, January 30, 1953; Maldonado-Koerdell, Inst. Mexicanos Recursos Nat. Renov., p. 130, 1953; Peters, Occas. Papers Mus. Zool. Univ. Michigan, 554:22, June 23, 1954; Duellman, Occas. Papers Mus. Zool. Univ. Michigan, 560:15, October 22, 1954; Webb and Fugler, Herpetologica, 13:35, March 30, 1957; Duellman, Occas. Papers Mus. Zool. Univ. Michigan, 589:15, March 21, 1958; Zweifel, Amer. Mus. Novitates, 1949:2, 5, June 17, 1959; Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 15(1):91-92, December 20, 1961.

_Conophis vittata_, Gadow, Proc. Zool. Soc. London, 2:196, 1905; Through Southern Mexico, p. 181, 1908.

_Conophis viduus_, Smith, Zool. Ser. Field Mus. Nat. Hist., 24:31, January 30, 1939; Hartweg and Oliver, Misc. Publ. Mus. Zool. Univ. Michigan, 47:26-27, July 13, 1940.

_Conophis vittatus viduus_, Smith, Journ. Washington Acad. Sci., 31:120-121, March 15, 1941; Proc. U. S. Natl. Mus., 92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:408, October 29, 1943; Woodbury and Woodbury, Journ. Washington Acad. Sci., 34(11):370, 1944; Smith and Taylor, Proc. U. S. Natl. Mus., 187:44, October 5, 1945; Univ. Kansas Sci. Bull., 33(pt. 2):340, March 20, 1950; Werler and Smith, Texas Journ. Sci., 4:565, fig. 16, December 30, 1952; Maldonado-Koerdell, Inst. Mexicanos Recursos Nat. Renov., p. 130, 1953; Davis and Dixon, Proc. Biol. Soc. Washington, 72:82-83, July 24, 1959.

_Conophis vittatus vittatus_ x _Conophis vittatus viduus_, Alvarez del Toro and Smith, Herpetologica, 12:13, March 6, 1956.

_Type._--Zoologisches Museum Berlin. Type locality not given, for the specimen was purchased from a dealer in Hamburg. The type locality was first restricted to "Acapulco," Guerrero, by Smith (1941:119), then to Laguna Coyuca, Guerrero, Mexico, by Smith and Taylor (1950:331).

_Diagnosis._--Three or four dorsal dark stripes, each involving two or more adjacent scale-rows; never having brown or black on the 1st scale-row; seven supralabials immaculate white or pale tannish-white.

_Variation._--One hundred seventy-one specimens have 149 to 181 (163.7 +- 6.33) ventrals. One hundred fifty-three of these having complete tails have 55 to 76 (64.8 +- 4.90) subcaudals; the number of ventrals plus subcaudals varies from 214 to 245 (228.5). In 170 specimens the reduction from 19 to 17 dorsal scales takes place between ventrals 84 and 118 (102.3 +- 6.60). Sexual dimorphism is evident in the number of subcaudals; 58 females have 55 to 66 (60.0) and 95 males have 59 to 76 (67.8) subcaudals. The longest specimen (AMNH 68004) is a male from Escurano, Oaxaca, Mexico, having a body length of 668 mm., a tail length of 182 mm. and a total length of 850 mm. A juvenile (CNHM 40435) from Tehuantepec, Oaxaca, Mexico, has a body length of 133 mm., a tail length of 31 mm. and a total length of 164 mm.

Variation in coloration is of such magnitude that it has been used as the basis for recognition of subspecies. Unfortunately, until this time, most specimens reported upon in the literature represented the two extremes of variation. After examining the coloration of 174 specimens with respect to geographic distribution, I conclude that only one highly variable species is represented. Specimens from the northern and western parts of the range (Michoacan, Colima, and Durango) have the color pattern of _C. vittatus_ as described by Peters (1860:518-521); these snakes have four narrow black stripes on a white or pale tan background, and an immaculate white venter. The lateral dark stripe, which on the head passes through the eye, is present on the dorsal half of the 3rd and the ventral half of the 4th scale-rows; the dorsolateral dark stripe, which passes along the middle of the head and splits on the nape, is present on the middle of the 8th scale-row. The other extreme in color pattern consists of three broad stripes; the two dorsolateral stripes are fused. This pattern is prevalent in specimens from the area around Tehuantepec, Oaxaca. The lateral stripes include the dorsal half to two-thirds of the 2nd, all of the 3rd and 4th, and half of the 5th scale-rows; the fused dorsolateral stripes sometimes cover all of the area dorsal to and including the dorsal third of the 7th scale-row.

Snakes from areas between Tehuantepec and the margins of the distribution of this species are variously intermediate between the extremes described above. In some snakes from these areas the lateral stripes are broad and include either the dorsal half of the 2nd scale-row or the ventral half of the 5th scale-row, but not both on the same specimen. Also, the dorsolateral stripes are broad and include most of the 9th and a part of the 10th scale-rows. Many specimens from the area around Tehuantepec, where the three-striped pattern is prevalent, have an intermediate pattern. Some have white on the center of the 10th scale-row or lateral stripes that are not so broad as to include the 3rd and 4th and half of each of the 2nd and 5th scale-rows.

The supralabials are immaculate white or pale tan, except that in some specimens the dorsalmost part of some supralabials are dark brown or black as they are included in the ventral boundary of the dark stripe that passes through the eye. There are no dusky markings on the chin or on any of the ventral scales.

There is no ontogenetic change in color pattern; juveniles have the same coloration as adults from the same geographic area.

Color in life is not greatly different from that of preserved specimens. One specimen (UMMZ 114483) from 10.8 miles south of Oaxaca, had in life black stripes, a pale yellowish tan dorsal ground-color and a pale off-white venter.

An excellent photograph of this species appears in Schmidt and Inger (1957:230) under the name _Conophis lineatus_.

_Remarks._--I have been unable to find variation of geographic importance in scutellation in this species. A wide range of variation in the characters of scutellation is present in specimens from most localities; it shows no significant clinal or geographic trends. As I have stated previously, in the discussion of variation, coloration has been the feature primarily used by previous workers to distinguish two "subspecies" for this species; _C. vittatus vittatus_ having four black stripes and _C. vittatus viduus_ having three black stripes. Most of the three-striped snakes occur in the vicinity of Tehuantepec, Oaxaca, whereas the four-striped snakes are found near the margins of the range of the species in Durango, Colima, Michoacan, Morelos and Puebla. Specimens that would have to be considered intergrades between the "subspecies" are found in Michoacan, Guerrero, Oaxaca and Chiapas. At the time the subspecies were proposed only specimens from Tehuantepec or from marginal areas were known. Utilizing the large number of specimens of this species presently available, geographic variation is found to be clinal, from those with three stripes from near Tehuantepec, through several intermediate patterns present on specimens from single localities in Guerrero, Oaxaca and Chiapas, to those with four dark stripes in areas farthest removed to the north and west from Tehuantepec. Since only coloration shows geographic variation, and since this variation represents a continuous cline, subspecies cannot be recognized for this species.

The presence and position of the three or four dark stripes on the body and the absence of brown on the 1st scale-row or on the ventral scales, in combination with the generic characters, distinguish _Conophis vittatus_ from all other Mexican snakes. The only other snake that occurs in western Mexico that has been confused with _C. vittatus_ is _Coniophanes piceivittus taylori_, which has 25, instead of 19, scale-rows.

_Distribution._--Semi-arid habitats on Pacific slopes from extreme southern Durango southeastward to Tuxtla Gutierrez, Chiapas, and inland in the eastern Balsas Basin to Morelos and western Puebla (fig. 5).

[Illustration: FIG. 5. Selected locality records for _Conophis vittatus_.]

_Specimens examined._--Total of 174, as follows: MEXICO: _no specific locality_, AMNH 66150-52, SU 9465. _Chiapas_: Piedra Parada, USNM 121453. _Pizo de Oro_, UIMNH 40821. Tuxtla Gutierrez, Parque Madero, UIMNH 37992-93, 38036-37. _Colima: no specific locality_, MCZ 46860, USNM 31394, 31396-97. 1 mi. SW Colima, AMNH 12783. S of Manzanillo, AMNH 19641. _Durango_: Hacienda de Gabriel, AMNH 14217. _Guerrero: Acahuizotla_, TCWC 7419, 9469. _1 mi. W Acahuizotla_, TCWC 7418. 3 mi. W Acapulco, AMNH 71626. _6 mi. E Acapulco_, TCWC 9476-77. _10 mi. S Acapulco_, TCWC 8578. _Agua del Obispo_, CNHM 104948, TCWC 11586. near Chilpancingo, MVZ 45067, UMMZ 85722-23. _1 mi. SW Colotlipa_, TCWC 9471-74. _2 mi. SW Colotlipa_, TCWC 9475. 14 mi. S Ixtapan de la Sal, KU 67648. _Laguna Coyuca_, CNHM 25881, UMMZ 80942. near La Union, AMNH 66337. _Magueyes, Laguna Coyuca_, AMNH 66149. _Playa Encantada_, TCWC 9470. 1 mi. S Tierra Colorada, KU 67649. near _Xaltinanguis, km. 405_, CNHM 104947. _Michoacan_: Coalcoman, UMMZ 104693. _1/2 mi. SE Coalcoman_, UMMZ 104492. _1 mi. N. Coalcoman_, UMMZ 112543. _1 mi. NE Coalcoman_, UMMZ 104692. Puerta de la Playa, UMMZ 105155. 12 mi. S Tzitzio (by road), UMMZ 99153. _Morelos: 12 km. NW Axochiapan_, TCWC 7311, UIMNH 17613, 25924. 7 mi. SE Cuernavaca, MVZ 32258. _Huajintlan, km. 133_, CNHM 103270. 12 km. S Puente de Ixtla, km. 133, CNHM 104949. _Oaxaca: Bisiliana_, AMNH 68010. _near Caoba, foot of Cerro Arenal_, AMNH 68009. _Cerro Arenal_, AMNH 68000-03. _Cerro de Laollaga_, UIMNH 36213. _Cerro de San Pedro_, UIMNH 17616. _Cerro Palma de Oro_, UIMNH 37116. "_C. Madrena, Sto. T. Quieri_," UIMNH 46904. near Chivela, MCZ 25021. Cinco Cerros, UIMNH 37114. _Dami Liesa_, AMNH 66877, UIMNH 6158, 37115. _Escuranos_, AMNH 66873-74, 68004-06. _Finca Santa Teresa, 2 km. NW Tehuantepec_, UMMZ 82648. _Huilotepec_, AMNH 66878, UIMNH 40820. _between Huilotepec and Tehuantepec_, AMNH 65106, UMMZ 82644-45. _Las Tejas_, UIMNH 6151-54. _Mixtequilla_, UIMNH 6157, 36211. _between Mixtequilla Mountains and Tehuantepec_, UMMZ 82652. _between Niltepec and "Carixxal,"_ AMNH 68876. 10.8 mi. SE Oaxaca, UMMZ 114483. _Quiengola_, UIMNH 17617. _between Quiengola Mountains and Tehuantepec_, UMMZ 82647. _Rancho Poso Rio, 6 km. S Tehuantepec_, UIMNH 6144-49, 37117-19, UMMZ 82649-51. _Rincon Bamba_, CNHM 105129-30, UIMNH 17615. _Salazar_, AMNH 66875. _vicinity of Salina Cruz_, UMMZ 82653. _San Geronimo_, AMNH 4306, CNHM 1457. _San Lucas Ixtepec_, UIMNH 36206. San Juan Lajarcia, UIMNH 36212. San Mateo del Mar, AMNH 65914. _San Pablo_, UIMNH 36207. _Santa Maria (Cerro de Liesa)_, AMNH 68011. Tapanatepec, MCZ 27806-11. Tehuantepec, AMNH 19644, 65107-09, 65907-13 plus 7, 66871-72, 66879, 68007-08, CNHM 40435-36, 105126-28, MCZ 46403, UIMNH 6150, 17614, 17618, 29692, 36208, 37120-21, UMMZ 82642-43, 82646, USNM 109709-14, _1-2 leagues SSE Tehuantepec_, UMMZ 82639-41. Tenango, UIMNH 36209-10. between Tlacolulita and Tequisistlan, CNHM 105125. _Yerba Santa_, UIMNH 6155-56. Puebla: Atencingo, KU 39626.

Skull

In studying the osteology of the genus _Conophis_, I have examined two complete skeletons (one _C. vittatus_ and one _C. lineatus_); two additional skulls of _C. vittatus_ and _C. lineatus_; and 24 sets of dentigerous bones, representing all of the species. Terminology of the skeletal elements is that of Duellman (1958), Parker (1878), Radovanovic (1937) and Szunyoghy (1932). The drawing of the right side of the skull of a specimen of _Tomodon lineatus_ that appears in Jan and Sordelli (1881:liv. 50, pl. 2, fig. 34) is of little value due to its small size and lack of detail.

The skull of _Conophis_ is typical of a relatively unspecialized colubrid snake. Skulls of _Conophis lineatus concolor_ and _C. vittatus_ closely resemble each other. The following description is based primarily on the skull of _C. lineatus concolor_ (UMMZ S-778).

The elements are discussed in the following order: nasal region, cranium and associated elements, maxillo-palatal-pterygoid arch, mandible, dentition, and vertebrae.

[Illustration: FIG. 6. The skull, lacking dentigerous bones, of _Conophis lineatus concolor_ (UMMZ S-788) showing (A) dorsal, (B) lateral, and (C) ventral views. x 3.]

_Nasal region._--The premaxillary is relatively heavy and has a concavity posteroventrally. The lateral processes slope downward, but remain fairly thick, and do not project far laterally. This shape (fig. 6) tends to strengthen the nasal region; this anterior strengthening may be a reflection of the fossorial habits of these snakes. There are no posterior processes of the premaxillary; thus the line of fusion with the nasals and septo-maxillaries is broad. The nasal plate is more than twice as long as wide. The nasals are relatively flat above, although each curves slightly downward medially and fuses into the medial nasal septum; laterally each nasal is narrower and deflected downward, forming a small dorsal shield over the nasal cavity. The septo-maxillaries are closely associated with the vomers and form the cavity in which the organ of Jacobson is situated. The broad medial part of the septo-maxillary forms the roof and anterior border of the cavity, whereas the anterior part of the vomer contains the main part of the capsule and forms the posterior and most of the lateral borders of the cavity. The vomer has a thin anterior ridge that gradually disappears before it reaches the border of the premaxillary. The vomer is approximately U-shaped, when viewed from below. It has no posterior process and does not articulate with the parasphenoid; there is a sizeable gap between the two bones. The septo-maxillary has a lateral process that terminally is directed slightly anteriorly.

_Cranium and associated elements._--The frontal is almost three times as long as it is wide; it is flat above with an emarginate dorsolateral margin that forms the upper limit of the optic capsule. Ventrally the frontal is concave and forms the median limits of the optic cavity. Farther ventrally the frontal joins with the parasphenoid, which at this place forms the ventral extent of the skull, and together with the basisphenoid forms the ventral part of the posterior three-fourths of the skull. In ventral aspect, the parasphenoid is a long, thin bone, slightly expanded anteriorly. It forms the anterior floor of the optic foramen; whereas the frontal forms the anterior roof of the same opening. The frontal and its septo-maxillary process surround the olfactory fenestra. The prefrontal articulates with the anterolateral process of the frontal. The posterior surface of the prefrontal forms the anterior wall of the orbit of the eye. The articulating surface upon which the median process of the maxillary bone rests is situated ventrally. The anterior dorsal surface of the prefrontal, together with the anterolateral edge of the frontal, extends slightly over the nasal cavity, affording some degree of protection for the contained organs and forming the posterior border of the cavity. A small nasal process also extends anteriorly from the ventrolateral surface of the prefrontal. The orbital-nasalis foramen is located in the anterior surface of the prefrontal. The parietals are fused into one large bone that forms the roof and sides of the middle part of the cranial cavity. From its suture with the frontal, the dorsal surface of the parietal is relatively flat in the area bounded laterally by the parietal crests, which extend posteromedially from the anterolateral corners of the bone and converge medially at a point near its posterior margin. A slight posterior extension of the parietal crests forms the supratemporal crest, which is present on the posterior part of the parietal and on the anterior part of the supraoccipital. The postfrontals are attached to the anterolateral processes of the parietal. Together the anterior surfaces of these two bones form the posterior rim of the orbit of the eye. The postfrontal extends laterally and ventrally and has a terminal extension that projects anterolaterally. In an articulated skull the trans-palatine articulates with the ventrolateral articulating surface of the postfrontal. Anteromedially, the parietal forms the roof and posterior margin of the optic foramen. The basisphenoid, which is fused with the parasphenoid, also forms a small part of the posteroventral margin of the optic foramen. The basisphenoid forms the floor of the middle part of the cranial cavity and the ventromedial down-pouching that contains the pituitary body. Posterolateral to the parietal and dorsal to the posterior part of the basisphenoid is the prootic. Laterally this bone is deeply emarginate; posteriorly it forms a large part of the otic notch, through which the columella passes. The columella is a long, thin bony rod that terminates posteriorly in cartilage. It is the cartilagenous part of the columella that connects with the external sound detecting mechanism. There are several foramina on the lateral surface of the prootic. On the anterolateral surface of the prootic, branches of the trigeminal nerve pass through three foramina whereas the facial nerve passes through the single posterior foramen near the otic notch. The squamosal is attached dorsoventrally to the posterior part of the parietal and to the lateral part of the prootic. At this place of attachment there is on the prootic a relatively heavy crest that forms a rather broad articulating base. The squamosal is long, flat, and curves slightly in a dorsal direction throughout its length; it becomes thinner and narrower posteriorly. The posterior third of the squamosal forms a broad base by means of which the squamosal articulates with the quadrate. The columella and the squamosal extend posteriorly beyond the limits of the braincase. Posteriorly the skull consists of four bones: an unpaired median dorsal supraoccipital, an unpaired median ventral basioccipital and two lateral exoccipitals. The basioccipital does not have noticeable pterygoid processes, but is rather smooth ventrally and only slightly emarginate on its posterolateral margins. Posteriorly, this bone forms the ventral part of the occipital condyle. The rest of the condyle, on each side, is formed by the exoccipitals. The exoccipitals also form part of the base to which the squamosal is attached. The exoccipitals extend around the sides of the foramen magnum and meet dorsally. Each exoccipital also forms the posterior part of the otic notch, which traverses the exoccipital. The exoccipitals bear moderate occipital crests that extend posterolaterally across the supraoccipital as branches from the supratemporal crest. The supraoccipital also has a medial crest that extends a short distance posteriorly from the supratemporal crest onto the exoccipitals at their dorsal line of fusion.

[Illustration: FIG. 7. The maxillo-palatal-pterygoid arch of _Conophis lineatus concolor_ (UMMZ S-788) showing (A) dorsal, (B) lateral, and (C) ventral views. x 3. Teeth shown by means of broken lines were represented only by their sockets.]

_Maxillo-palatal-pterygoid arch._--In an articulated skull, the anterior edge of the maxillary is immediately posterior to the lateral tip of the premaxillary (fig. 7). The maxillary is curved moderately laterally and is not robust at its tip, but it becomes heavier about one-third of its length posteriorly. A dorsomedian process begins at about one-third of its distance from the anterior end; the prefrontal articulates with this process. The process is broad and almost flat, except that at its medial end, an elongate, rounded knob extends ventrally. The dorsomedian process of the maxillary extends toward, but does not meet, a lateral process from the palatine. The maxillary teeth are set in sockets on the ventral surface of the bone. Just posterior to the level of the last prediastemal tooth is the median trans-palatine process that articulates with the anteromedian part of the trans-palatine. Immediately posterior to this process, the maxillary narrows slightly; then it broadens to form an obliquely oriented knob. The posteroventral surface of the posterior knob of the maxillary bears one or two enlarged maxillary teeth. (These teeth are discussed further in the section on Dentition.) The anterolateral part of the trans-palatine articulates with the dorsal surface of the posterior knob of the maxillary. Toward the middle of its length, the trans-palatine narrows considerably; then it broadens again and articulates with the pterygoid. The palatine is slightly rounded at its anterior end, which extends anteriorly to the posterior margin of the vacuity containing Jacobson's organ. The palatine extends posteriorly to the trans-palatine process of the maxilla, where the palatine articulates with the pterygoid. A posterior pterygoid process from the palatine projects posteromedially from the end of the palatine and overlaps the anterior end of the pterygoid. Just less than one-half the distance from the anterior end of the palatine, there is a lateral process that curves ventrolaterally forming a blunt tip posteriorly. Slightly more posteriorly and on the medial side of the palatine, is a medial sphenoid process, which is thin, rather broad, and curves ventromedially; ultimately it comes to lie near the anterior part of the parasphenoid. The palatine teeth are set in shallow sockets on the ventral edge of the bone. Of the bones of the maxillo-palatal-pterygoid arch, those on the pterygoid extend farthest posteriorly. The pterygoid is broad medially and posteriorly, although pointed at its posterior tip. The trans-palatine articulates in a broad line at about one-third of the distance along the lateral margin of the pterygoid. Immediately posterior to this articulation, there is a median ridge on the pterygoid; lateral to the pterygoid ridge is an abrupt hollow, the pterygoid groove. Posteromedially, this groove becomes gradually more shallow and disappears. The dorsal surface of the pterygoid is rounded anteriorly and somewhat flattened posteriorly, whereas the ventral surface is gently rounded along its length, except that there is a high median crest. The pterygoid teeth are situated in shallow sockets along this crest. The teeth diminish in size posteriorly.

[Illustration: FIG. 8. The left mandible and associated quadrate of _Conophis lineatus concolor_ (UMMZ S-788) showing (A) lateral and (B) medial views. x 3. Teeth shown by means of broken lines were represented only by their sockets.]