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140 results for “snake systematics”
Fig. 3 in The Nomenclature And Systematics Of Some Australasian Homalopsid Snakes (Squamata: Serpentes: Homalopsidae)
Fig. 3. The paratype of M. resetari, BMNH 1935.7.65.2. A: shows the enlarged occipital scales (O) and their relationship to the temporal (T). B: illustrates the single preocular scale. C: illustrates the three pairs of chin shields with the 3rd pair longer than wide. D: illustrates the edge of the ventral scales (V) and first 3 dorsal rows and the keels on the scales above dorsal row 3.
Fig. 1 in The Nomenclature And Systematics Of Some Australasian Homalopsid Snakes (Squamata: Serpentes: Homalopsidae)
Fig. 1. The maximum likelihood tree of the Homalopsidae from Alfaro et al. (2008), modified to show that Australasia has been colonized by at least three lineages of homalopsid snakes (Australasian Icon Map): one colonization by the lineage that gave rise to the coastal Australian bockadam, Cerberus australis; one colonization by the coastal crab-eating snake, Fordonia leucobalia and; one colonization by the lineage that gave rise to both the coastal Myron species as well as the freshwater Enhydris polylepis (and probably C. annulata and Heurnia ventromaculata). The other lineages shown on the tree are South Asian or Southeast Asian.
Fig. 2 in The Nomenclature And Systematics Of Some Australasian Homalopsid Snakes (Squamata: Serpentes: Homalopsidae)
Fig. 2. The holotype of Myron karnsi, SMF 19569. A and B: show the overall of head plates. C: illustrates the enlarged occipital scales (O) and their relationship to the temporal (T). D: has the three pair of chin shields numbered and the 3rd pair is as wide as long.
Phylogenomics of fresh and formalin specimens resolves the systematics of old world mud snakes (Serpentes: Homalopsidae) and expands biogeographic inference
<p>The known biodiversity of Asia and Australasia is continuously expanding with more focused studies on systematics of various groups and the respective biogeography. Historically, fluctuating sea-levels and cyclic connection and separation of now-disjunct landmasses have been invoked to explain the accumulation of biodiversity via species pump mechanisms. However, recent research has shown that geological shifts of the mainland and dispersal events may be better explanations of the biodiversity in these regions. We investigate these processes using the poorly-studied and geographically widespread Mud Snakes (Serpentes: Homalopsidae) using a target capture approach of ~4,800 nuclear loci from fresh tissues and supplemental mitochondrial data from formalin tissues from museum specimens. We use these datasets to reconstruct the first resolved phylogeny of the group, identify their biogeographic origins, and test hypotheses regarding the roles of sea-level change and habitat selection on their diversification. Divergence dating and ancestral range estimation yielded support for an Oligocene origin and diversification from mainland Southeast Asia and Sundaland in the rear-fanged group ~20 million years ago, followed by eastward and westward dispersal. GeoHiSSE models indicate that niche expansion of ancestral rear-fanged lineages into aquatic environments did not impact their diversification rates. Our results highlight that Pleistocene sea-level changes and habitat specificity did not primarily lead to the extant species richness of Homalopsidae, and that, alternatively, geological shifts in mainland Southeast Asia may be a major driver of diversity in this group. We also emphasize the importance of using fresh and degraded tissues, and both nuclear and mitochondrial DNA, for filling in knowledge gaps in poorly known, but highly diverse and conceptually important groups, constituting a non-traditional model study system for understanding transitions between terrestrial, marine, and freshwater environments.</p>
Fig. 9 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 9. Dipsas oreas (Cope). A typically banded specimen from northern Peru (ANSP 31778). The snake is in a defensive posture (see under Defensive Behaviors in the Dipsadini).
Fig. 17 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 17. Defensive behavior of Sibon argus (AMNH 115927) from 600 m on the continental divide north of El Cope´, Cocle´, Panama. Top: The head is widened when mildly disturbed. Bottom: When further harassed, the snake coiled its body into a symmetrically raised spring, keeping its head hidden in the center.
Fig. 21 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 21. The final stage of defensive behavior in Dipsas nicholsi—a raised coil narrowest at the top, with the head exposed. Over a period of several days, this snake consistently coiled in the same direction (counterclockwise following the coils from above). See figure 1 for another view of the same specimen.
Fig. 5 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 5. Dipsas nicholsi (Dunn) from Madden Forest, central Panama. Left: KU 110311 in dorsal and ventral view. Right: KU 110312, above; KU 110313, below.
Fig. 1 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 1. Dipsas nicholsi (Dunn), a snaileater endemic to central Panama. Top: A specimen (not collected) photographed in 1974 in the Madden Forest Preserve, by Harry W. Greene. Bottom: Another specimen from Madden Forest, this one in a final stage of defense posturing (see figs. 20–21), photographed in 1966 by C.W. Myers.
Fig. 3 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 3. Dipsas variegata (Duméril, Bibron, and Duméril). Representative specimens in dorsal and ventral view. Left: D. v. variegata from Rancho Grande, Venezuela (FMNH 204479, 468 mm SVL). Right: D. v. trinitatis from near Asa Wright Nature Center, Trinidad (FMNH 217217, 419 mm SVL).
Fig. 13 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 13. Dipsas andiana (Boulenger) in dorsal and ventral view. Left: Specimen from Bolívar Province, Ecuador (KU 132503). Right: Specimen from Pichincha province, Ecuador (MCZ 166543).
Fig. 2 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 2. Variation in dorsal head patterns of Dipsas variegata (Duméril, Bibron, and Duméril). From top to bottom: AMNH 111075 (Bolívar, Venezuela), AMNH 137584 (Trinidad), AMNH 21275 (Guyana), AMNH 114769 (Bolívar, Venezuela). The cephalic color pattern of Dipsas variegata, which varies from indistinct to blotched, lacks the distinctive Πshaped marking that characterizes D. nicholsi and D. andiana (cf. figs. 4, 8).
Fig. 15 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 15. Dipsas andiana (Boulenger). A specimen of unknown locality (AMNH 79013) with an atypical head pattern. See text.
Fig. 19 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 19. Complex defensive behavior in Sibynomorphus mikanii. Top: The head is raised and widened, and the body is inflated, especially obvious at the widened neck (which approaches the dorsoventral hood formation of some snakes). Middle: After continued provoking, the snake has deflated the body and arranged itself into a loose asymmetrical coil or ball, with its head hidden. Bottom: An alternative coil at another time, with the head almost hidden.
Fig. 20 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 20. Initial stages in the defensive coiling of Dipsas nicholsi (KU 110313). Top: Beginning formation of an anterior coil (stage 1). Bottom: Anterior coil complete, posterior coil initiated (stage 2). See text for behavioral sequence in which stage 2 above is replaced by abrupt whipping motions while retaining the forward coil. See figure 21 for stage 3, in which the snake has gathered itself into a single coil.
Fig. 16 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 16. Head widening (triangulation)—the temporary acquisition of triangular head shape by spreading the jaw articulations—a common defensive trait among the Dipsadini and some other snakes. This behavior can also be seen in figures 9 and 17–19. Top: Dipsas viguieri from lowland Madden Forest, central Panama (KU 110317). Bottom: Dipsas temporalis from cloud forest on ridge between Río Jaqué and Río Imamadó, 800– 890 m, Darién, Panama (specimen one of KU 110294–110297).
Fig. 12 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 12. Comparison of head shapes and color patterns in Dipsas andiana and Dipsas oreas at equivalent magnifications. Top: D. andiana (KU 132503, 622 mm total length). Bottom: D. oreas (KU 142803, 629 mm total length). Dipsas andiana has a stereotypical Πshaped pattern on the dorsal surface and is relatively unmarked otherwise, whereas D. oreas has irregularly and heavily pigmented dorsal and lateral surfaces of the head. Dipsas oreas also has angular canthal and supratemporal regions and a relatively longer postorbital region than does D. andiana.
Fig. 18 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 18. Defensive behavior of Sibon nebulatus from the Río, Jaque´, 1.5 km above Río Imamado´, 50 m, Darién, Panama (KU 112474). Top: An initial stage with posteriorly widened head. Middle: Passive coil with widened head exposed. Bottom: An alternative coil with head (still widened) concealed.
Fig. 8 in Systematics of Snakes Referred to Dipsas variegata in Panama and Western South America, with Revalidation of Two Species and Notes on Defensive Behaviors in the Dipsadini (Colubridae)
Fig. 8. Dipsas andiana (Boulenger). Closeup of head of holotype. The characteristic Πshaped pattern differentiates andiana from Dipsas oreas and hints at a possible relationship with Panamanian Dipsas nicholsi.
FIG. 4 in The Herald Snakes (Crotaphopeltis) of the Central African Republic, including a systematic review of C. hippocrepis
FIG. 4. — Crotaphopeltis hippocrepis, juvenile (BMNH 1932.9.1.3) showing white occiput. Scale bar: 5 mm. Photo Geert Brovad.
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