Eunectes Wagler, 1830

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

Eunectes Wagler, 1830

Material examined.

Eunectes murinus (Linnaeus, 1758) (ISEZ R/103; ISEZ R/265; ISEZ R/266; MNCN 15385; ZFMK 5179); Eunectes notaeus Cope, 1862 (SMF PH 60; SMF PH 70).

Description (Figs 92-95).

Trunk vertebrae. Vertebrae very large, massive, and robust; centrum much shorter than wide; cotyle and condyle slightly depressed; neural arch moderately vaulted; posterior median notch of the neural arch deep; neural spine much higher than long; prezygapophyseal accessory processes short; hypapophyses disappearing between V 60 and V 70; haemal keel in more posterior vertebrae well-developed, ridge-like, produced posteriorly; paracotylar foramina absent.

Lee and Scanlon (2002) treated the foramina at the edges of the postzygapophyses in posterior view as parazygantral foramina. Such small foramina are also present in our here presented material, though they are smaller than the ones presented by Lee and Scanlon (2002: fig. 10K). See Discussion below for more details on this feature.

Trunk / caudal transition. The last trunk vertebrae bear a (plate-like) hypapophysis that is retained (spur-like) in all cloacal vertebrae and first caudal vertebra. Paired haemapophyses first appear on the second caudal vertebra.

Number of vertebrae. Eunectes murinus (ZFMK 5179): 313 (252+4+57) including a final fusion; Eunectes notaeus (SMF PH 60): 323 (271+5+47); Eunectes notaeus (SMF PH 70): 295 (235+3+57).

Data from literature: Eunectes deschauenseei Dunn & Conant, 1936: 238 trunk vertebrae plus 3 cloacal vertebrae plus 45 caudal vertebrae ( Machado-Filho 2020); Eunectes murinus : 252 trunk vertebrae plus 59 cloacal and caudal vertebrae ( Polly et al. 2001); Eunectes murinus : 249 trunk vertebrae plus unknown number of cloacal and caudal vertebrae ( Tsuihiji et al. 2012); Eunectes murinus : 233-248 trunk vertebrae plus 3-4 cloacal vertebrae plus 68 caudal vertebrae ( Machado-Filho 2020); Eunectes murinus : 247-259 trunk vertebrae plus 68-72 cloacal and caudal vertebrae ( Nopcsa 1923); Eunectes notaeus : 235 trunk vertebrae plus 4 cloacal vertebrae plus 52 caudal vertebrae ( Machado-Filho 2020); Eunectes notaeus : 238 trunk and cloacal vertebrae plus 65+ caudal vertebrae ( Alexander and Gans 1966).