Boa Linnaeus, 1758

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

Boa Linnaeus, 1758

Material examined.

Boa constrictor Linnaeus, 1758 (HNHM 2004.77.1; ISEZ R/102; ISEZ R/104; ISEZ R/106; ISEZ R/110; ISEZ R/457; MGPT-MDHC 175 (juvenile); MGPT-MDHC 500; MNCN 15988; SMF PH 35; SMF PH 36; SMF PH 37; SMF PH 40; SMF PH 41; SMF PH 42; SMF PH 43; SMF PH 44; SMF PH 45 (juvenile); SMF PH 46; SMF PH 57; SMF PH 220).

Description (Figs 80-85).

Trunk vertebrae. Centrum much shorter than wide; cotyle and condyle orbicular; neural arch vaulted; posterior median notch of the neural arch deep; neural spine much higher than long in most trunk vertebrae; prezygapophyseal accessory processes short; hypapophyses disappearing between the 60th and 70th vertebrae; haemal keel in more posterior vertebrae well-developed, ridge-like; paracotylar foramina present.

Georgalis and Scheyer (2019) highlighted the substantial modification of the shape and thickness of the zygosphene during ontogeny in Boa .

Trunk / caudal transition. Distinct hypapophyses that appear in the two last trunk vertebrae (in SMF PH 40, these distinct hypapophyses appear even earlier in more preceding trunk vertebrae), diminish gradually in size in succeeding cloacal vertebrae; it is reduced to an indistinct haemal keel in the last (or two last) cloacal vertebrae and the anteriormost caudal vertebrae. Haemapophyses first appear on the third caudal vertebra; sometimes they are unpaired (unilateral), followed by normally developed (paired) structures on the following caudal vertebrae.

Number of vertebrae (all for Boa constrictor ): SMF PH 44: 346 (271+4+71); SMF PH 37: 321 (254+5+62); SMF PH 57: 312 (246+4+62 [posteriormost caudal vertebrae fused]); MGPT-MDHC 500: 310 (255+4+51, including a final fusion); SMF PH 36: 309 (249+4+56); SMF PH 40: 309 (248+4+57); SMF PH 45 (juvenile): 305 (246+4+55); MGPT-MDHC 175 (juvenile): 298 (245+5+48); ISEZ R/457: 294+ (258+5+31+); SMF PH 35: 252 trunk vertebrae (cloacal and caudal vertebrae missing); SMF PH 46: 245 trunk vertebrae (cloacal and caudal vertebrae missing).

Data from the literature and unpublished data from personal communications: Boa constrictor : 302-310 vertebrae in total ( Parmley and Reed 2003); Boa constrictor : 305 vertebrae in total, among which 60 cloacal and caudal vertebrae ( Owen 1850, 1877); Boa constrictor : 228 trunk and cloacal vertebrae plus 56 caudal vertebrae (Jingsong Shi, unpublished data, personal communication to GLG); Boa constrictor : 250 trunk vertebrae plus 8 cloacal vertebrae (apparently erroneous) plus 44 caudal vertebrae ( Rochebrune 1881); Boa constrictor : 226-248 trunk vertebrae plus 4-5 cloacal vertebrae plus 31-50 caudal vertebrae ( Machado-Filho 2020); Boa constrictor : 246 trunk vertebrae plus 59 cloacal and caudal vertebrae ( Nopcsa 1923); Boa constrictor : 237 trunk vertebrae plus 5 cloacal vertebrae plus 42 caudal vertebrae ( Albino 2011); Boa imperator Daudin, 1803: 237-244 trunk vertebrae plus 4-5 cloacal vertebrae plus 47-60 caudal vertebrae ( Machado-Filho 2020).

It should be noted that Boa constrictor has recently been recognized as a species complex, with other cryptic species recognized ( Reynolds et al. 2014; Card et al. 2016; Reynolds and Henderson 2018); therefore, it is not certain whether all these dry skeletons (in particular specimens that were collected during the 18th, 19th, and/or early 20th centuries) that were studied by us or were mentioned in older literature, belong indeed to Boa constrictor or some other species.