Eryx Daudin, 1803

Szyndlar, Zbigniew & Georgalis, Georgios L., 2023, An illustrated atlas of the vertebral morphology of extant non-caenophidian snakes, with special emphasis on the cloacal and caudal portions of the column, Vertebrate Zoology 73, pp. 717-886 : 717

Eryx Daudin, 1803

Material examined.

Eryx colubrinus (Linnaeus, 1758) (ISEZ R/370; MGPT-MDHC 172; SMF PH 24; SMF PH 203 [juvenile]; SMF PH 204 [juvenile]; UF Herp 151340 [Morphosource.org: Media 000476408, ark:/87602/m4/476408]; UMMZ 190384; UMMZ 190339; ZFMK 50246); Eryx conicus (Schneider, 1801) (ISEZ R/360; NHMUK 1930.5.8.13; NHMUK 1964.1224; MNHN-ZA-AC-1907.0319; SMF PH 18; UMMZ 18380; UMMZ 190949; UMMZ 128037); Eryx elegans (Gray, 1849) (AMNH R143761 [formerly SIZNASU Oph. 1650/4151]); Eryx jaculus (Linnaeus, 1758) (ISEZ R/15; ISEZ R/250; ISEZ R/264 [juvenile]; ISEZ R/321; NHMW 21520; NHMUK 1920.1.20.1526); Eryx jayakari Boulenger, 1888 (NHMUK 1909.10.15.8); Eryx johnii (Russell, 1802) (ISEZ R/330; NHMUK 1930.5.8.26; NHMUK 1930.5.8.27; NHMUK 1930.5.8.28; NHMUK 1930.5.8.30; MNHN-AC-1912.0418; MNHN-ZA-AC-1872.0059; SMF PH 20); Eryx miliaris (Pallas, 1773) (SIZNASU uncat.; Tokar Coll. 1117; Tokar Coll. 1119; UMMZ 190697); Eryx muelleri (Boulenger, 1892) (CAS Herp 136230); Eryx somalicus Scortecci, 1939 (MSNS 5250); Eryx tataricus (Lichtenstein in Eversmann, 1823) (ISEZ R/482; SIZNASU uncat.; Tokar Coll. 1116).

Description (Figs 103-108).

Trunk vertebrae. Centrum wider than long; cotyle and condyle orbicular; neural arch depressed; posterior median notch of the neural arch deep; neural spine low or of medium height (the tallest neural spine is found in Eryx johnii , according to Underwood [1976]); prezygapophyses much dorsally inclined in anterior view, with prezygapophyseal articular facets situated above the base of the neural canal; prezygapophyseal accessory processes short except for Eryx jayakari in which they are long; hypapophyses disappearing usually at the level of ca. 50th vertebra; haemal keel in Eryx conicus and Eryx colubrinus broad and well developed, in other species weakly developed or absent; paracotylar foramina absent.

Trunk / caudal transition. Last trunk and anterior cloacal vertebrae provided either with hypapophysis ( Eryx colubrinus ) or either with no distinct subcentral structures. Haemapophyses appear on the 1st to 5th caudal vertebrae. Posterior caudal vertebrae display highly complex morphology: they are provided with additional apophyses unknown in other snakes, serving for articulation. The most complex morphology is observed in Eryx miliaris and the simplest (in fact, extremely simple as for Eryx standards) is in Eryx elegans . In Eryx johnii , zygosphenes and zygantra are absent from the posterior caudal vertebrae. A detailed description of the caudal osteology of Eryx will be presented elsewhere.

Number of vertebrae. Eryx colubrinus (UF Herp 151340): 213 (185+3+25, including a final fusion); Eryx colubrinus (SMF PH 24): 212 (178+3+31); Eryx colubrinus (ZFMK 50246): 206+ (184+4+18+ [posteriormost caudal vertebrae missing]); Eryx colubrinus (UMMZ 190339): 204 (174+3+27, including a final fusion); Eryx colubrinus (MGPT-MDHC 172): 202 (171+3+28, including a final fusion); Eryx colubrinus (ISEZ R/370): 195 (170+4+21, including a final fusion); Eryx conicus (UMMZ 190949): 204 (176+3+25, including a final fusion); Eryx conicus (UMMZ 128037): 198 (171+4+23, including a final fusion); Eryx conicus (SMF PH 18): 191 (169+4+18 [plus a final fusion]); Eryx conicus (NHMUK 1930.5.8.13): 20 caudal vertebrae, including a final fusion (trunk and cloacal vertebrae missing); Eryx elegans (AMNH R143761): 207 (177+3+27, including a final fusion); Eryx jaculus (NHMUK 1920.1.20.1526): 193 (160+4+29, including a final fusion); Eryx jaculus (ISEZ R/15):?3 cloacal vertebrae plus 25 caudal vertebrae, including a final fusion (trunk vertebrae missing); Eryx jayakari (NHMUK 1909.10.15.8): 3 cloacal vertebrae plus 25+ caudal vertebrae, including a final fusion (most trunk and some posteriormost caudal vertebrae missing); Eryx johnii (SMF PH 20): 246 (217+3+26, including a final fusion); Eryx johnii (ISEZ R/330): 240 (219+5+16, including a final fusion); Eryx johnii (NHMUK 1930.5.8.30): 4 cloacal vertebrae plus 34 caudal vertebrae, including a final fusion (number of trunk vertebrae unknown); Eryx johnii (MNHN-ZA-AC-1872.0059): 3 cloacal vertebrae plus 21 caudal vertebrae, including a final fusion (number of trunk vertebrae unknown); Eryx miliaris (UMMZ 190697): 198 (177+4+17, including a final fusion); Eryx miliaris (SIZNASU uncat.): 3 cloacal vertebrae plus 25 caudal vertebrae, including a final fusion (trunk vertebrae missing); Eryx miliaris (Tokar Coll. 1117): 2 cloacal vertebrae plus 25 caudal vertebrae, including a final fusion (trunk vertebrae missing); Eryx miliaris (Tokar Coll. 1119): 3 cloacal vertebrae plus 21 caudal vertebrae, including a final fusion (trunk vertebrae missing); Eryx muelleri (CAS Herp 136230): 210 (183+4+23, including a final fusion); Eryx somalicus (MSNS 5250): 3 cloacal vertebrae plus 18+ caudal vertebrae (number of trunk vertebrae unknown and posteriormost caudal vertebrae missing); Eryx tataricus (ISEZ R/482): ~191 (~168+4+19+ [posteriormost caudal vertebrae missing]); Eryx tataricus (Tokar Coll. 1116): 28+ caudal vertebrae (trunk, cloacal, and posteriormost caudal vertebrae missing).

Data from literature and unpublished data from personal communications: Eryx colubrinus : 187-190 trunk and cloacal vertebrae plus 28-29 caudal vertebrae ( Alexander and Gans 1966); Eryx conicus : 190 trunk and cloacal vertebrae plus 18+ caudal vertebrae ( Alexander and Gans 1966); Eryx jaculus : 174-185 trunk and cloacal vertebrae plus 19 caudal vertebrae ( Alexander and Gans 1966); Eryx jaculus : 175-185 trunk vertebrae plus 27-33 cloacal and caudal vertebrae ( Nopcsa 1923); Eryx jaculus : 193 trunk vertebrae plus 9 cloacal vertebrae (apparently erroneous) plus 20 caudal vertebrae ( Rochebrune 1881): Eryx jaculus : 210 vertebrae in total (NHMC80.3.114.20; Petros Lymberakis, personal communication to GLG); Eryx johnii : 208 trunk vertebrae plus 3 cloacal vertebrae plus unknown number of caudal vertebrae ( Gasc 1974); Eryx johnii : 4 cloacal vertebrae and 31 caudal vertebrae ( Sood 1941); Eryx miliaris : 210 trunk and cloacal vertebrae plus 26 caudal vertebrae (IVPP OV 2728; Jingsong Shi, unpublished data, personal communication to GLG).

An interesting feature of Eryx is a very low variation in the total number of vertebrae within the genus.