Aquatic Snake Blog

Beni Anaconda, Eunectes beniensis, Dirksen 2002

Eunectes beniensis Dirksen 2002. Type Locality: Trinidad, Beni, Bolivia. Holotype: AMNH 101924. Eunectes beniensis is known from relative few specimens from northern Bolivia. The largest specimen was a 3.2 m female. It is known to use aquatic situations in open habitats. It is similar in appearance to the Green Anaconda, Eunectes murinus. Read more

March 26, 2016
Green Anaconda, Eunectes murinus (Linnaeus 1758)

Boa murina Linnaeus 1758:215. Type locality: “America.” Holotype: NHRM Lin. 9. Boa scytale Linnaeus 1758:214 Boa anacondo Daudin, 1803:161 Boa aquatica Wied-Neuwied:824 Eunectes murinus — Wagler 1830:167 Boa gigas Latreille 1801:136 Eunectes scytale – Stull:389 Eunectes barbouri Dunn and Conant 1936:504 Eunectes murinus murinus – Dunn, 1944:183 Eunectes murinus gigas — Dunn, 1944:183 Distribution and Habitat. The Green Anaconda is endemic to the Amazon Basin… Read more

March 26, 2016
Yellow Anaconda, Eunectes notaeus, Cope 1862

Eunectes notaeus Cope 1862: 70. Type Locality: Paraguay River and confluents. Holotype: USNM 4707. Eunectes murinus Peracca 1895 Eunectes wieningeri Steindachner 1903 Eunectes notaeus — Kahl et al. 1980: 207 Distribution and Habitat: The Yellow Anaconda ranges from about 15°S in Bolivia and Brazil to 32°S in Argentina. It inhabits wetlands, including; swamps, seasonal floodplains, palm savanna, marshes, gallery… Read more

March 26, 2016
De Schauensee’s Anaconda, Eunectes deschauenseei, Dunn and Conant, 1936

Eunectes deschauenseei Dunn and Conant, 1936, Holotype: ANSP 20891. Type Locality: Probably Marajo Island at the mouth of the Amazon. Distribution and Habitat. The species inhabits swamps and seasonally flooded habitats in the Brazialian states of Amapa and Para, including the mouth of the Amazon and the Ilha de Marajo. It also occurs in French Guiana… Read more

March 26, 2016
Tentacled Snake, Erpeton tentaculatus

Erpeton tentaculatus Lácèpede, 1800: 169. Holotype: MNNH. Type locality: none given. Rhinopirus tentaculatus: Merrem, 1820: 82. Homalopsis herpeton: Schlegel, 1837a, 2: 359. Herpeton tentaculatum: Jan and Sordelli, 1860: 1, pl. 1. Herpeton herpeton: Giebel, 1861: 110. Distribution: Southern Thailand, Cambodia, southern Vietnam (Murphy, 2007). Diagnosis: Prominent paired rostral appendages; dorsal scales in 34 – 39 at… Read more

March 26, 2016

The most basal Thamnophiine clade recovered by Zaher et al. (2019) included the Liodytes, Clonophis, Haldea, and Virginia genera. These are a mixture of fossorial, terrestrial, and semi-aquatic species. Clonophis exploits an unusual aquatic habitat – crayfish burrows; both Haldea and Virginia are small fossorial species. Liodytes contain some of the most aquatic North American snakes.
The ancestor of North American natricids immigrated from Eurasia sometime before the early Miocene (~19–18 Ma). We know this because the earliest known Western Hemisphere natricid fossils date to the early Miocene, and we know they shared an ancestor because of shared anatomy and DNA.

There are no highly specialized aquatic pythons that converge with the anacondas – the highly aquatic boas. However, some python species are best considered semi-aquatic. The largest pythons (Malayopython reticulatus, Python sebae, Python natalensis, Python bivittatus) use aquatic situations to hunt and thermoregulate. The largest pythons are habitat generalists, but they are also frequently associated with water. The large body size may be possible because of their buoyance in water, making movement more efficient.

The highly aquatic and unique file snakes have loose, baggy skin and minor, rough scales, each with sensory organs. Their short tails are round, prehensile, flat, and sword-like; the eyes and valvular nostrils are dorsally or dorsolateral. Their lack of muscle tone is spectacular and can only be fully appreciated by handling one, a physiological feature restricting them to an entirely aquatic lifestyle. The rough, file-like surface of the skin and its loose folds are used in catching and holding slippery, mucus-covered fish. Their maxillary teeth are similar in size, long, and fluted on the sides and posterior surfaces. The fluted condition is found in many fish-eating snakes.

The two species that compose the genus Farancia are considered some of the most aquatic snakes in North America, but both species are known to wander overland (Steen et al. 2013). Droughts may trigger their movement from a wetland, and excessive rainfall may also trigger their movement. Females will also move overland to nest. Both species take aquatic prey. Semlitsch et al. (1988) have described juvenile emergence in both the Fall and Spring and note that hatchlings may benefit from Fall emergence by feeding before their first winter. However, Fall emergence may present the hatchlings with dried or reduced aquatic habitats, while spring emergence would have abundant habitat and food (larval salamanders).
The members of the genus are known to have maternal attendance of eggs, a highly specific diet of elongated prey, American eels (Anguilla rostrata), and the eel-like salamanders of the genera Siren and Amphiuma.

The largest boas, the highly aquatic anacondas (Eunectes), are relatively well known. The oldest and largest member of the clade (Titanoboa) was aquatic, and today, the most aquatic members of the family are the anacondas of the genus Eunectes.

Anacondas are Neotropical snakes found east of the Andes. Four extant species and one fossil species compose the genus. The clade includes the largest snake, the Green Anaconda, Eunectes murinus, which reaches at least 8 m and has the greatest mass (in females) of any extant snake (250 kg). Eunectes is derived from a Greek word that means “good swimmer.” The aquatic habitats of these snakes are well documented. Pizzatto et al. (2007) found an aquatic habitat to be a synapomorphy for this genus. The large body size, a relatively long tail, and the dorsal positioning of the eyes and nares are all traits associated with life in water.

Aquatic Snake Blog

Beni Anaconda, Eunectes beniensis, Dirksen 2002

Green Anaconda, Eunectes murinus (Linnaeus 1758)

Yellow Anaconda, Eunectes notaeus, Cope 1862

De Schauensee’s Anaconda, Eunectes deschauenseei, Dunn and Conant, 1936

Tentacled Snake, Erpeton tentaculatus