Posts tagged madagascar.

markscherz:

Pseudoxyrhopus tritaeniatus Mocquard, 1894

Distribution

This species is known to occur along the length of the eastern rainforest belt of Madagascar, from Masoala in the north to Andohahela in the south.

Morphology & Colouration:

Pseudoxyrhopus tritaeniatus is among the largest members of the genus Pseudoxyrhopus, reaching lengths of up to one metre. It is characterised by 25 dorsal scale rows at midbody, a character it shares with only two other congeners, P. microps and P. ankafinaensis.

The colouration of P. tritaeniatus is striking and unique in Madagascar, reminding somewhat of Oreocryptophis porphyraceus coxi. The snake is typically red, with four or five black dorsal stripes.

Habits:

Pseudoxyrhopus tritaeniatus is a nocturnal, terrestrial snake. It is known to eat rodents, but its diet may consist of other mammals, small reptiles, and possibly fish and birds if it can get them. During the day, it is known to seek shelter under rotten wood.

Conservation Status:

Pseudoxyrhopus tritaeniatus is currently listed as Least Concern on the IUCN Red List, due to its wide distribution inside well protected areas.

Systematics and Taxonomy:

Pseudoxyrhopus tritaeniatus is unmistakable. It is not currently clear which species are its closest relatives, but it is quite possible that Pmicrops is among them, given its similarities in scale counts, size, and overall appearance.

Phylogeny:

Animalia-Chordata-Reptilia-Serpentes-Lamprophiidae-Pseudoxyrhophiinae-Pseudoxyrhopus-P. tritaeniatus

First photo by Sara Ruane, second by leopardcat, third by Bernard Dupont.

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09.18.14 ♥ 71

markscherz:

Lycodryas citrinus (Domergue, 1995)

Distribution:

Lycodyas citrinus is found in dry forests in western Madagascar, most notably Beroboka, Kirindy, Namoroka, and Tsingy de Bemaraha.

Morphology & Colouration:

Lycodryas citrinus is a long, thin tree snake, reaching a maximum total length of around 70 cm. The body is characterised by 17 dorsal scale rows at midbody, 239-254 ventrals, 111-126 undivided or partly divided subcaudals, 8 supralabial scales, one loreal, and a divided anal scale. 

This species is undoubtedly Madagascar’s most bright and distinctive snake species, unable to be confused with any other species. The body is a vibrant yellow, with 50-58 dark crossbands.

Habits:

Like all members of the genus LycodryasL. citrinus is arboreal and nocturnal, and feeds mostly on small vertebrates, potentially including frogs, lizards, and possibly young birds.

One female in captivity gave birth to two 18-20 cm long young in the Malagasy rainy season (December) (Vences et al. 1998).

Conservation Status:

Lycodryas citrinus is currently listed as Vulnerable on the IUCN Red List. It has a limited distribution (<7000 square kilometres), is suffering from habitat reduction, and is being collected for the pet trade.

Systematics and Taxonomy:

Lycodryas citrinus was transferred to the genus Lycodryas from Stenophis by Nagy, Glaw & Vences, 2010 on the basis of its genetic affinities. It is most closely related to an undescribed Lycodryas species from northeastern Madagascar (Marojejy).

Phylogeny:

Animalia-Chordata-Reptilia-Serpentes-Lamprophiidae-Lycodryas-L. citrinus

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References:

Nagy, Z.T., F. Glaw & M. Vences (2010) Systematics of the snake genera Stenophis and Lycodryas from Madagascar and the Comoros. Zoologica Scripta 39(5):426-435

Vences, M., F. Glaw & W.B. Love (1998) Live bearing in the snake Stenophis citrinus from Madagascar. British Herpetological Society Bulletin 64:13-14

09.06.14 ♥ 138

markscherz:

Geckolepis maculata Peters, 1880

Distribution:

Geckolepis maculata is generally considered to be distributed widely around Madagascar, and only truly absent from the south west of the island (Köhler et al. 2009). It is found in rainforest, littoral forest, and deciduous forest. It is not found at altitudes exceeding 650 m above sea level. Geckos conforming to the strict definition of G. maculata are only found in northern Madagascar (Lemme et al. 2012).

Morphology & Colouration:

Geckolepis maculata is a medium-sized gecko, though the largest member of the genus Geckolepis. It reaches body lengths of up to 8 cm, with its tail as long or longer again. The innermost postmental scales contact one another (an important diagnostic character, though not completely reliable). It possesses 22-25 scale rows at mid-body. 

The body colour is brownish, often marked with brown spots in adults. Juveniles can be more colourful. A lateral head streak is usually present.

Habits:

Geckolepis maculata is an arboreal, nocturnal species. It typically roosts beneath loose bark on dead trees, or the dead leaf axils of Ravenala trees, up to a height of 5 metres above the ground. It eats a variety of insects. Eggs are laid under tree bark or beneath stones as well. These geckos may aestivate, storing fat in the base of their tails.

Conservation Status:

Geckolepis maculata is listed as Least Concern by the IUCN Red List, due to its widespread distribution and abundance.

Systematics and Taxonomy:

The taxonomy of the genus Geckolepis is complicated. G. humbolti, from the Comoros, is considered a junior synonym of G. maculata, as it does not differ strongly in any morphometric characters. It can be distinguished from G. typica by its larger size, postmental scales in contact as opposed to without contact, and more midbody scale rows. It can be distinguished from G. polylepis by its larger size, fewer scale rows at midbody, fewer ventral cale rows, and lack of longitudinal dark lines.

Characters given here are those corresponding to clade AB from Lemme et al. (2012), as this is probably the clade that refers to the original G. maculata sensu stricto. It is thought that at least 9 other species of Geckolepis exist, meaning that seven remain to be described, so affinities are still unclear.

Phylogeny:

Animalia-Chordata-Reptilia-Gekkonidae-Geckolepis-G. maculata

First photo by Jon Boone, second by Pagale Bacha, third by Cowyeaw

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References:

Köhler, G., H.-H. Diethert, R.A. Nussbaum and C.J. Raxworthy. 2009. A revision of the fish scale geckos, genus Geckolepis Grandidier (Squamata, Gekkonidae) from Madagascar and the Comoros. Herpetologica 65:419-435

Lemme, I., M. Erbacher, N. Kaffenberger, M. Vences and J. Köhler. 2012. Molecules and morphology suggest cryptic species diversity and an overall complex taxonomy of fish scale geckos, genus Geckolepis. Organisms Diversity & Evolution 13:87-95

08.04.14 ♥ 133

markscherz:

Geckolepis typica Grandidier, 1867

Distribution:

Geckolepis typica is generally considered to be broadly distributed across southern and western Madagascar, ranging as far north as Mahajanga, and as far east as the Anosy Mountains, but never particularly far inland (Köhler et al. 2009). It is a low-altitude specialist, and is not found above 650 m above sea level. Its habitat consists of a variety of dry and spiny forests. Geckos belonging to the strict G. typica (clade K in Lemme et al. 2012) are only found in southern Madagascar.

Morphology & Colouration:

Geckolepis typica has a medium-sized gecko, not exceeding 53 mm in body length. The tail is usually as long as or longer than the body. The innermost postmental scales do not make substantial contact with one another (this is important). It possess 28-32 scale rows at midbody. Like all Geckolepis species, it has large scales covering slippery skin, and these are shed easily upon capture to facilitate its escape.

The body colouration is uniform grey/brown, occasionally with longitudinal dark lines, but without heavy dark spots.

Habits:

Geckolepis typica is an arboreal, nocturnal species. It typically roosts beneath loose bark on dead trees, or, less commonly, under rocks at the base of trees. It eats a variety of insects. Eggs are laid under tree bark or beneath stones as well. These geckos may aestivate, storing fat in the base of their tails.

Conservation Status:

Geckolepis typica is listed as Least Concern by the IUCN Red List, as it is widely distributed and is quite common.

Systematics and Taxonomy:

The taxonomy of the genus Geckolepis is complicated. G. anomala and G. petiti were moved into synonymy with G. typica by Köhler et al. (2009), and generally differed from G. typica only in characters of the postmental scale arrangement. G. typica is smaller than G. maculata and has fewer scale rows at mid body. It is larger than G. polylepis, and that species also has its postmental scales in broad contact, unlike those of G. typica.

Geckolepis typica is thought to refer to clade K from Lemme et al. (2012). It is clear that at least three species from this genus remain undescribed, with a possible diversity of up to 10 total species. Characters here are therefore given for G. typica sensu stricto, and reference to Lemme et al. (2012) is recommended.

Phylogeny:

Animalia-Chordata-Reptilia-Gekkonidae-Geckolepis-G. typica

First photo by Mark Scherz, second by Alejandro Lozano.

Click here to see more TaxonFiles!

References:

Köhler, G., H.-H. Diethert, R.A. Nussbaum and C.J. Raxworthy. 2009. A revision of the fish scale geckos, genus Geckolepis Grandidier (Squamata, Gekkonidae) from Madagascar and the Comoros. Herpetologica 65:419-435

Lemme, I., M. Erbacher, N. Kaffenberger, M. Vences and J. Köhler. 2012. Molecules and morphology suggest cryptic species diversity and an overall complex taxonomy of fish scale geckos, genus Geckolepis. Organisms Diversity & Evolution 13:87-95

07.16.14 ♥ 115

markscherz:

libutron:

Giant Leaftail Gecko | ©Giovanni Mari  (Nosy Mangabe, Madagascar)

Endemic to Madagascar, the Giant Leaftail Gecko or Common Flat-tail Gecko, Uroplatus fimbriatus (Gekkonidae) can reach a total length of 330 mm. This large nocturnal gecko, is found in eastern Madagascar and on the islands Nosy Bohara and Nosy Mangabe.

According to the assessment of the IUCN Red List of Threatened Species (2013.2):

There is uncertainty about the number of species represented under the names Uroplatus fimbriatus and U. giganteus (F. Glaw and M. Vences pers. comm. January 2011). Raxworthy et al. (2008) consider U. giganteus to be a synonym for U. fimbriatus; however it has also been argued that additional undescribed species may be revealed within U. giganteus and/or U. fimbriatus by future molecular study (F. Glaw pers. comm. January 2011).

The scheme followed here is that of Glaw et al. (2006), which considers this group to consist of two species, U. fimbriatus and U. giganteus, which correspond to the southern and northern clades of U. fimbriatus respectively (Raxworthy et al. 2008; F. Glaw, pers. comm. January 2011).

Due to the geographical proximity of the U. fimbriatus type locality, Nosy Mangabe, to genetic U. giganteus, further research is needed to establish whether the assignment U. fimbriatus to the southern clade treated here under that name is valid, or whether this name should instead be applied either to a single species including both presently recognized clades, or to a northern form presently included under the name U. giganteus (C. Raxworthy pers. comm. January 2011).

This situation is a little clearer now:

In 2013, Ratsoavina et al. performed a diversity assessment of the genus Uroplatus. They showed, among other things, that one species (U. ebenaui) is actually ~9 cryptic speciesThey considered all of thegiant leaftails from Nosy Mangabe southward as U. fimbriatus, and U. giganteus northward of Nosy Mangabe. They did, however, highlight the fact that far more data will be needed before their taxonomic situation can be cleared up.

Ratsoavina, F.M., N.R. Raminosoa, E.E. Louis Jr., A.P. Raselimanana, F. Glaw and M. Vences. 2013. An overview of Madagascar’s leaf tailed geckos (genus Uroplatus): species boundaries, candidate species and review of geographical distribution based on molecular data. Salamandra 49:115-148

markscherz:

libutron:

Langaha madagascariensis male | ©Olaf Pronk

Langaha madagascariensis (Colubridae), commonly called Madagascar leaf‐nosed snake, is endemic to Madagascar, as its common and scientific names point out.

Langaha is a medium-sized, slender, arboreal, mostly diurnal Malagasy colubrid genus comprised of three species, all of which can be quickly identified by the presence of a large leaf like rostral appendage.

A report published in 2008 demonstrates that L. madagascariensis is a potentially harmful snake capable of envenoming humans.

*capable of envenomating scientists who purposefully allow the snake to chew on their hand for a little bit to see the effect of its venom. These snakes are not dangerous at all; certainly no more so than
Heterodon spp., and almost infinitely harder to find.

IUCN “Species of the Week”: Angel’s Chameleon (Furcifer angeli) [x]

05.02.14 ♥ 75

markscherz:

Calumma tarzan Gehring, Pabijan, Ratsoavina, Köhler, Vences & Glaw, 2010

The Tarzan Chameleon

Distribution:

Calumma tarzan is found in only a tiny area of fragmented forest in central eastern Madagascar.

Morphology & Colouration:

Calumma tarzan is a medium-sized chameleon, reaching a maximum total length of 15 cm. It possesses a unique rostral ornamentation, consisting of a small spade-like projection, which is larger in males than females.

Ground colouration ranges from green to bright yellow. In males, the back of the head and neck are brown to blackish in colouration. When stressed, dark transverse bands appear along the body. A single white/yellow spot is present on each flank. A pair of white ventral bands runs the length of the body, as is typical for the C. furcifer group of chameleons.

Habits:

Like most chameleons, C. tarzan is an arboreal, diurnal species. It roosts at night at the tips of branches at a height of 1-4 metres above the ground - apparently lower in juveniles.

Conservation Status:

Calumma tarzan is currently listed as Critically Endangered in the IUCN Red List. It is thought to inhabit an area of less than 10km2, which is under heavy threat from deforestation.

Taxonomy:

Calumma tarzan does not closely resemble any other chameleon species, even those it is most closely related to, because of its unique rostral appendage, and stress colouration. A population of chameleons from a nearby forest fragment was described by Gehring et al. (2010), which may be conspecific with C. tarzan, but this remains unclear.

Phylogeny:

Animalia-Chordata-Reptilia-Squamata-Chameleonidae-Calumma-C. tarzan

Photos are of the male holotype of the species, from Gehring et al. 2010.

Click here to see more TaxonFiles!

References:

Gehring, P.-S., M. Pabijan, F.M. Ratsoavina, J. Köhler, M. Vences & F. Glaw (2010) ‘A Tarzan yell for conservation: a new chameleon, Calumma tarzan sp. n., proposed as a flagship species for the creation of new nature reserves in Madagascar' Salamandra 46(3):167-179

03.23.14 ♥ 54

markscherz:

rhamphotheca:

TSA Turtle Tuesday: Spider Tortoise

Did you know that the spider tortoise (Pyxis arachnoides) gets its common name from the beautiful pattern on its shell that resembles a spider web?

Endemic to the dry, coastal areas of western and southern Madagascar, this small tortoise is partial to eating grasses, young leaves, and succulent plants, as well as insects. This shy chelonian is most active during the wet season (November through April) when the vegetation that it thrives on is lush. During the dry season, the spider tortoise buries itself deep in the sand and becomes dormant as the weather gets colder. This is believed to be an energy saving mechanism which allows the tortoise to retain necessary moisture until the wet season and the lush vegetation returns!

The TSA has been active in conservation programs in Madagascar, specifically with critically endangered spider tortoises and radiated tortoises, since 2007… read more here.

(via: Turtle Survival Alliance)

One of Madagascar’s four endemic tortoise species. They are also sometimes called pixie tortoises because they are are so small and adorable.

palaeopedia:

The Malagasy leaf-nosed snake, Langaha madagascariensis (1790)
Phylum&#160;: ChordataClass&#160;: ReptiliaOrder&#160;: SquamataSuborder&#160;: SerpentesFamily&#160;: ColubridaeGenus&#160;: LangahaSpecies&#160;: L. madagascariensis
Least concern
90 cm long (size)
Madagascar (map)
Malagasy leaf-nosed snake is a medium-sized highly cryptic arboreal species. It is endemic to Madagascar and found in deciduous dry forests and rain forests. There is considerable sexual dimorphism within the species; the males are dorsally brown and ventrally yellow with a long tapering snout while the females are mottled grey with a leaf shaped snout.
Malagasy leaf-nosed snake is largely a sit-and-wait predator. It may show curious resting behaviour, hanging straight down from a branch.
Malagasy leaf-nosed snake is generally calm and reluctant to bite unless provoked. Envenomation by the snake causes severe pain in humans but is not deadly.

palaeopedia:

The Malagasy leaf-nosed snake, Langaha madagascariensis (1790)

Phylum : Chordata
Class : Reptilia
Order : Squamata
Suborder : Serpentes
Family : Colubridae
Genus : Langaha
Species : L. madagascariensis

  • Least concern
  • 90 cm long (size)
  • Madagascar (map)

Malagasy leaf-nosed snake is a medium-sized highly cryptic arboreal species. It is endemic to Madagascar and found in deciduous dry forests and rain forests. There is considerable sexual dimorphism within the species; the males are dorsally brown and ventrally yellow with a long tapering snout while the females are mottled grey with a leaf shaped snout.

Malagasy leaf-nosed snake is largely a sit-and-wait predator. It may show curious resting behaviour, hanging straight down from a branch.

Malagasy leaf-nosed snake is generally calm and reluctant to bite unless provoked. Envenomation by the snake causes severe pain in humans but is not deadly.

03.15.14 ♥ 35

hyacynthus:

Liophidium pattoni from Miinala (2011).

Miinala, M. 2011. New location record for the recently described Liophidium pattoni (Vieites, Ratsoavina, Randrianiaina, Nagy, Glaw & Vences, 2010). Herpetology Notes 4:181.

IUCN [info]

03.14.14 ♥ 61

hyacynthus:

Malagasy Tree snake (Stenophis betsileanus), Vohimana reserve, Madagascar by Frank.Vassen on Flickr.

Parastenophis betsileanus - the genus changed from Stenophis based on the work of Nagy et al. 2010.

Nagy, Z. T., Glaw, F. & Vences, M. 2010. Systematics of the snake genera Stenophis and Lycodryas from Madagascar and the Comoros. Zoologica Scripta 39:426–435.

astronomy-to-zoology:

Giant Malagasy Hognose Snake (Leioheterodon madagascariensis)

…a large species of Hognose Snake that is native to Madagascar and the Nosy Be, Nosy Saktia and Comoros Islands. True to their common name L. madagascariensis is quite large and can reach lengths of around 180 cm (6 ft). L. magagascariensis is diurnal and occupies a wide range of habitats, including humid and dry forests, shrublands and grasslands. They feed mainly on small birds and rodents, and are known to take reptile eggs as well.

Classification

Animalia-Chordata-Reptilia-Squamata-Colubridae-Leioheterodon-L. madagascariensis

Image: Frank Vassen

02.25.14 ♥ 418

markscherz:

Uroplatus phantasticus (Boulenger, 1888)

The Satanic Leaf-tailed Gecko.

Distribution:

These geckos are found throughout much of the rainforest belt spanning Madagascar’s eastern side. The holotype of the species is from ‘southern central eastern’ Madagascar.

Morphology and Colouration:

These geckos receive their common name from their large superciliary spines (eyebrow spines).

The bodies of the U. ebenaui-group of geckos (U. ebenaui, U. phantasticus, U. finiavana, U. malama, and at least four undescribed species) are laterally compressed (as opposed to the dorso-ventrally compressed form of all other members of the genus). This makes them highly effective leaf-mimics.

Colouration in this species is extremely variable. Generally, however, a dark line extends from the posterior of the head down the dorsal mid-line. The iris is silvery in its periphery and reddish-brown towards the centre, but this too varies to some extent.

These geckos are characterized by a large tail that is roughly half or equal to the full length of the body of the geckos. There is a moderate degree of sexual dimorphism: females tend to lack serration in the tail. Males can have either serrated or non-serrated tail edges, but extensive serration appears to be entirely restricted to males.

Uroplatus phantasticus cannot regenerate its tail once lost.

Habits:

Uroplatus phantasticus is a nocturnal, arboreal gecko species.

These geckos rely on their extremely cryptic colouration and morphology to shelter from predation during the day. At rest, they typically hold their tails alongside their bodies, hiding their feet beneath them, for maximum crypsis.

At night, these geckos typically hunt between ground level and three metres up. Often they are observed at night hanging from branches in the position seen in the third photo above.

Curiously, these geckos, and indeed the rest of the Uroplatus genus, are unable to run like most geckos. Instead, if they are in need of rapid locomotion, they leap in a frog-like fashion.

Conservation Status:

Uroplatus phantasticus is listed as Least Concern on the IUCN Red List due to its wide distribution and occurrence in several well protected areas of rainforest.

Taxonomy:

Uroplatus phantasticus is superficially similar to all of the other members of the U. ebenaui-group. The following characteristics however set it apart from other members of the clade: U. phantasticus has a blackish oral mucosa, setting it apart from U. finiavana. It is also larger in size and has a larger tail than that species. It also lacks an armpit, which sets it apart from U. ebenaui. The tail is also much larger than that of U. ebenaui, and the head smaller in proportion to the body. The body possesses a large number of spines, which set it apart from the smooth-skinned U. malama. In most other respects, U. malama and U. phantasticus are highly similar.

The U. ebenaui-group’s taxonomy is still complicated and at least four species remain to be described.

Phylogeny:

Animalia-Chordata-Reptilia-Squamata-Gekkonidae-Uroplatus-U. phantasticus

First two photos by Olaf Pronk. Third photo by Mark Scherz. Fourth photo by Paul Bertner.

Click here to see more TaxonFiles!

02.24.14 ♥ 464
What would be the explanation for the absence of pythons in Madagascar?

Asked by libutron

markscherz:

This is a fantastic question, and one that is rather contentious, and takes quite a lot of answering. So I’m sorry this has taken weeks to put together, but here is the extremely long answer to the question:

Until recently, it was believed that mainland Africa had only pythons and a single group of boas (sandboas, genus Eryx), while the rest of the boas boas were restricted to the Americas and Madagascar.

Madagascar’s large constricting snakes were assigned in their early descriptions to the Boidae. Indeed, so alike are Madagascar’s boas to those of the Americas that it misled phylogenetic reconstructions of them:

In 1991, based solely on morphological characters (molecular phylogenetics was in its infancy), Kluge found Acrantophis and Sanzinia to be sister to the South American genus Boa. And so he synonymised them, transferring the Malagasy boas to the South American genus, thus rendering a genus Boa with the following members: Boa constrictor (and subspecies thereof), B. madagascariensis, B. dumerili, and B. manditra - Sanzinia madagascariensis obviously couldn’t become Boa madagascariensis, because Acrantophis madagascariensis had already taken that name, so he erected a new name for this species.

As it turns out, moving Madagascar’s boas to the genus Boa was a huge mistake. But Madagascar’s boas are boas (Family Boidae: Subfamily Sanziniinae), they just don’t belong in the genus Boa. A phylogeny produced by Noonan & Chippindale (2006a) showed that the genus Boa belongs to a neotropical clade, together with Epicrates, Eunectes, and Corallus. These are closest related to a group containing Afro-Indian Eryx plus Candoia from Papua New Guinea. These together are then related to the North and Central American boas (Exiliboa+Lichanura+Charina). Finally, sister to this whole group of New World+Australiasian boas is a clade containing Calabaria, Acrantophis, and Sanzinia. This whole group is formalised as Boidae, and is sister to the Pythonidae in the Noonan & Chippindale phylogeny.

Until this point, Calabaria were thought to be allied to pythons and not to boas, but the molecular work of this and subsequent studies showed that to be quite incorrect. So boom, another group of boas is present in Africa. Woo.

All subsequent phylogenies (and several earlier ones that I can’t be bothered to go find) have supported this view that Madagascar’s boas belong in their own genera (Sanzinia and Acrantophis), and yet still Wikipedia would have you believe that they are in Boa. I will fix this in the next few weeks, but in the mean time, ignore it. Focus on my argument here.

In light of more complete taxonomic and genetic sampling by Pyron et al. (2013), it was shown that boas and pythons aren’t even sister groups (which we knew before, but never with quite such nice resolution and such high taxon sampling). Rather Boidae+Calabaridae are sister to a group containing Anomochilidae+Cylindrophiidae+Uropeltidae+Xenopeltidae+Loxocemidae+Pythonidae. Together, these two clades comprise the superfamily Henophidia (ancient snakes), which is paraphyletic with regards to all other snakes except the blind snakes, but shh we can ignore that for now.

Anyway, the important thing is that both of these reports (Noonan & Chippindale 2006a and Pyron et al. 2013) agree on one key point: Madagascar’s boas are unequivocally the oldest radiation of boas.

How, then, did Madagascar’s boas get to Madagascar? Well, Noonan & Chippindale (2006a, 2006b) suggested a vicariant origin; that they were in Madagascar when it broke off from Gondwana as it split. This vicariant origin is further supported by the rapid diversification in deep branches in the boids (Noonan & Chippindale 2006a).

However, the age of the African clade (Calabaria+Acrantophis+Sanzinia) suggested by Noonan & Chippindale (2006a, 2006b) is 30 million years after Madagascar lost contact with Antarctica, and through Antartica, South America; and 11 million years after Madagascar lost contact with India and became isolated (Samonds et al. 2013). It would be prudent therefore to interpret this as either incorrect inferrence by Noonan & Chippindale in both papers, or indication of oceanic dispersal. I lean towards the results of Noonan & Chippindale being wrong because of the way they calculated their clade ages (poor outgroup choice with an incorrect date).

After the split from Africa, Madagascar maintained connection with India and, through a land bridge connecting to Antarctica, was connected to South America, and could continue to exchange species with it for at least a few million years (Noonan & Chippindale 2006a; Samonds et al. 2013). This left Madagascar with its own boas, one of which apparently dispersed to Africa to give rise to Calabaria. Not until much later did Madagascar’s modern boa genera arise on the island.

Today, most authors (e.g. Pyron et al. 2013; Reynolds et al. 2014) tend to assume that Calabaria, which is a troublesome group, genetically, is actually basal to all boas, and do not include it in the true boas. They do not, however ,make any comment on the implications of this, in terms of origins.

Bizarrely, the Round Island Boa (Casarea dussumieri) is not related to those of Madagascar at all (Round Island is very close to Madagascar - just north of Mauritius), but is instead most closely related to a Malaysian lineage, and only distantly related to other constrictors at all (Reynolds et al. 2014). How it fits into this picture is very unclear.

The implication then is that pythons and boas split long before Madagascar broke off from Africa. Very recent (read: not yet physically published but available online) research by Reynolds et al. (2014) has suggested an origin for the modern pythons in what is today northern Africa, whence they then spread south, north, and east. The boas, on the other hand, are suggested to have arisen in southern Gondwana by some authors (Reynolds et al. 2014) and Asia by others (Noonan & Sites 2010).

But the problem is that Reynolds et al. (2014), and indeed all authors working on the relationships of the Henophidian snakes, have not attempted to figure out where and when the other families arose. Thus, we have no idea where the ancestors were at the time of the split of Gondwana. All we can postulate is that Madagascar had boas when it split off (perhaps getting them after Africa was isolated from the rest of Gondwana via land bridges to Antarctica+South America; Samonds et al. 2013), while pythons were further up in Africa somewhere. Then, when pythons radiated down into Africa, they didn’t make it across to Madagascar - or if they did, they went extinct soon afterwards.

tl;dr: Nobody knows for sure. Nobody has really even tried to find out. Probably because it’s not a very interesting question (relatively speaking).

References:

Kluge, A. G. (1991) ‘Boine snake phylogeny and research cycles' Miscellaneous Publications, Museum of Zoology, University of Michigan 178:1-58

Noonan, B. P. & P T. Chippindale (2006a) ‘Dispersal and vicariance: The complex evolutionary history of boid snakes' Molecular Phylogenetics and Evolution 40:347-358

Noonan, B. P. & P T. Chippindale (2006b) ‘Vicariant Origin of Malagasy Reptiles Supports Late Cretaceous Antarctic Land Bridge' The American Naturalist 168(6):730-741

Noonan, B. P. & J. W. Sites Jr. (2010) ‘Tracing the origins of iguanid lizards and boine snakes of the Pacific' The American Naturalist 175(1):61-72

Pyron, R. A., F. T. Burbrink & J. J. Wiens (2013) ‘A phylogeny and revised classification of Squamata, including 4161 species of lizards and snakes' BMC Evolutionary Biology 13:93

Reynolds, R. G., M. L. Niemiller & L. J. Revell (2014) ‘Toward a Tree-of-Life for the boas and pythons: Multilocus species-level phylogeny with unprecedented taxon sampling' Molecular Phylogenetics and Evolution 71:201-213

Samonds, K. E., L. R. Godfrey, J. R. Ali, S. M. Goodman, M. Vences, M. R. Sutherland, M. T. Irwin & D. W. Krause (2013) ‘Imperfect isolation: factors and filters shaping Madagascar’s extant vertebrate fauna' PLoS One 8(4):e62086

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