Molecular phylogeny of elapid snakes and a consideration of their biogeographic history

Evolutionary relationships among the major elapid clades, particularly the taxonomic position of the partially aquatic sea kraits (Latkauda) and the fully aquatic true sea snakes have been the subject of much debate. To discriminate among existing phylogenetic and biogeographic hypotheses, portions of both the 16S rRNA and cytochrome b mitochondrial DNA genes were sequenced from 16 genera and 17 species representing all major elapid snake clades from throughout the world and two non-elapid outgroups. This sequence data yielded 181 informative sites under parsimony. Parsimony analyses of the separate data sets produced trees of broad agreement although less well supported than the single most parsimonious tree resulting from the combined analyses. These results support the following hypotheses: (1) the Afro-Asian cobra radiation forms one or more sister groups to other elapids, (2) American and Asian coral snakes form a clade, corroborating morphological studies, (3) Bungarus forms a sister group to the hydrophiines comprised of Latkauda, terrestrial Australo-Papuan elapids and true sea snakes, (4) Latkauda and true sea snakes do not form a monophyletic group but instead each group shares an independent history with terrestrial Australo-Papuan elapids, corroborating previous studies, (5) a lineage of Melanesian elapids forms the sister group to Latkauda, terrestrial Australian species and true sea snakes. In agreement with previous morphologically based studies, the sequence data suggests that Bungarus and Latkauda represent transitional clades between the elapine 'palatine erectors' and hydrophiine 'palatine draggers'. Both intra and inter-clade genetic distances are considerable, implying that each of the major radiations have had long independent histories. I suggest an African, Asian, or Afro-Asian origin for elapids as a group, with independent Asian origins for American coral snakes and the hydrophiines.     

Inferring Species Trees from Gene Trees: A Phylogenetic Analysis of the Elapidae (Serpentes) Based on the Amino Acid Sequences of Venom Proteins

Toward the goal of recovering the phylogenetic relationships among elapid snakes, we separately found the shortest trees from the amino acid sequences for the venom proteins phospholipase A₂and the short neurotoxin, collectively representing 32 species in 16 genera. We then applied a method we term gene tree parsimony for inferring species trees from gene trees that works by finding the species tree which minimizes the number of deep coalescences or gene duplications plus unsampled sequences necessary to fit each gene tree to the species tree. This procedure, which is both logical and generally applicable, avoids many of the problems of previous approaches for inferring species trees from gene trees. The results support a division of the elapids examined into sister groups of the Australian and marine (laticaudines and hydrophiines) species, and the African and Asian species. Within the former clade, the sea snakes are shown to be diphyletic, with the laticaudines and hydrophiines having separate origins. This finding is corroborated by previous studies, which provide support for the usefulness of gene tree parsimony.     

Phylogeny of Australasian venomous snakes (Colubroidea, Elapidae, Hydrophiinae) based on phenotypic and molecular evidence

Scanlon, John D. & Lee, Michael S. Y. (2004). Phylogeny of Australasian venomous snakes (Colubroidea, Elapidae, Hydrophiinae) based on phenotypic and molecular evidence. — Zoologica Scripta , 33 , 335–366.
Phylogenetic relationships among Hydrophiinae (Australasian and marine elapid snakes) are inferred using 87 characters from external, skeletal, hemipenial and internal anatomy, ecology, and chromosomes as well as available sequences of two mitochondrial genes (cytochrome b and 16S rRNA). Parsimony analysis of the combined data retrieves many widely accepted clades; while observed bootstrap or branch (Bremer) support for these is often weak, most have never been corroborated previously by a rigorous numerical analysis. Sea kraits ( Laticauda ) and Solomon Islands elapids are basal to the remaining hydrophiines (Australian terrestrial forms and hydrophiin sea snakes). The latter clade includes three main lineages: a large-bodied oviparous lineage, a small-bodied oviparous lineage, and a viviparous lineage (which also includes the hydrophiin sea snakes, strongly reaffirmed as monophyletic). While the Solomons retain a relictual fauna, New Guinea has less endemism and has been invaded multiple times by Australian lineages, so there is no clear 'stepping stone' pattern supporting a northern (Asian, rather than Gondwanan) biogeographical origin.     

An immunological assessment of the phylogenetic position of New World coral snakes

The New World coral snakes (micrurines), genera Micrurus and Micruroides have recently been seen as derived from a lineage of South American colubrids, rather than from a common lineage with Old World elapids and sea snakes as traditionally accepted. We compared serum albumins of representative coral snakes, Old World elapids, sea snakes, and neotropical colubrids immunologically. Phylogenetic analysis of the biochemical data unambiguously allies the micrurines with the family Elapidae as it is currently understood. Using the albumin molecular clock calibration derived from other terrestrial vertebrates. we suggest a late Oligocene-early Miocene separation between the New and Old World elapid lineages. This requires a movement of elapid stocks from Asia into North America, and supporting evidence for this model is derived from several paleontological sources. We suggest that a number of extant micrurine lineages have had long independent histories.     

Phylogenetic analysis of the grape family (Vitaceae) based on three chloroplast markers

Seventy-nine species representing 12 genera of Vitaceae were sequenced for the trnL-F spacer, 37 of which were subsequently sequenced for the atpB-rbcL spacer and the rps16 intron. Phylogenetic analysis of the combined data provided a fairly robust phylogeny for Vitaceae. Cayratia, Tetrastigma, and Cyphostemma form a clade. Cyphostemma and Tetrastigma are each monophyletic, and Cayratia may be paraphyletic. Ampelopsis is paraphyletic with the African Rhoicissus and the South American Cissus striata nested within it. The pinnately leaved Ampelopsis form a subclade, and the simple and palmately leaved Ameplopsis constitutes another with both subclades containing Asian and American species. Species of Cissus from Asia and Central America are monophyletic, but the South American C. striata does not group with other Cissus species. The Asian endemic Nothocissus and Pterisanthes form a clade with Asian Ampelocissus, and A. javalensis from Central America is sister to this clade. Vitis is monophyletic and forms a larger clade with Ampelocissus, Pterisanthes, and Nothocissus. The eastern Asian and North American disjunct Parthenocissus forms a clade with Yua austro-orientalis, a species of a small newly recognized genus from China to eastern Himalaya. Vitaceae show complex multiple intercontinental relationships within the northern hemisphere and between northern and southern hemispheres.     

Molecular phylogeny and divergence dates for Australasian elapids and sea snakes (hydrophiinae): evidence from seven genes for rapid evolutionary radiations

One of the most prolific radiations of venomous snakes, the Australo-Melanesian Hydrophiinae includes approximately 100 species of Australasian terrestrial elapids plus all approximately 60 species of viviparous sea snakes. Here, we estimate hydrophiine relationships based on a large data set comprising 5800 bp drawn from seven genes (mitochondrial: ND4, cytb, 12S, 16S; nuclear: rag1, cmos, myh). These data were analysed using parsimony, likelihood and Bayesian methods to better resolve hydrophiine phylogeny and provide a timescale for the terrestrial and marine radiations. Among oviparous forms, Cacophis, Furina and Demansia are basal to other Australian elapids (core oxyuranines). The Melanesian Toxicocalamus and Aspidomorphus group with Demansia, indicating multiple dispersal events between New Guinea and Australia. Oxyuranus and Pseudonaja form a robust clade. The small burrowing taxa form two separate clades, one consisting of Vermicella and Neelaps calanotus, and the other including Simoselaps, Brachyurophis and Neelaps bimaculatus. The viviparous terrestrial elapids form three separate groups: Acanthophis, the Rhinoplocephalus group and the Notechis-Hemiaspis group. True sea snakes (Hydrophiini) are robustly united with the Notechis-Hemiaspis group. Many of the retrieved groupings are consistent with previous molecular and morphological analyses, but the polyphyly of the viviparous and burrowing groups, and of Neelaps, are novel results. Bayesian relaxed clock analyses indicate very recent divergences: the approximately 160 species of the core Australian radiation (including sea snakes) arose within the last 10 Myr, with most inter-generic splits dating to between 10 and 6 Ma. The Hydrophis sea snake lineage is an exceptionally rapid radiation, with > 40 species evolving within the last 5 Myr.     

Uncoupling ecological innovation and speciation in sea snakes (Elapidae, Hydrophiinae, Hydrophiini)

The viviparous sea snakes (Hydrophiini) are by far the most successful living marine reptiles, with ～ 60 species that comprise a prominent component of shallow-water marine ecosystems throughout the Indo-West Pacific. Phylogenetically nested within the ～ 100 species of terrestrial Australo-Melanesian elapids (Hydrophiinae), molecular timescales suggest that the Hydrophiini are also very young, perhaps only ～ 8-13 Myr old. Here, we use likelihood-based analyses of combined phylogenetic and taxonomic data for Hydrophiinae to show that the initial invasion of marine habitats was not accompanied by elevated diversification rates. Rather, a dramatic three to six-fold increase in diversification rates occurred at least 3-5 Myr after this transition, in a single nested clade: the Hydrophis group accounts for ～ 80% of species richness in Hydrophiini and ～ 35% of species richness in (terrestrial and marine) Hydrophiinae. Furthermore, other co-distributed lineages of viviparous sea snakes (and marine Laticauda, Acrochordus and homalopsid snakes) are not especially species rich. Invasion of the oceans has not (by itself) accelerated diversification in Hydrophiini; novelties characterizing the Hydrophis group alone must have contributed to its evolutionary and ecological success.     

Higher-level snake phylogeny inferred from mitochondrial DNA sequences of 12S rRNA and 16S rRNA genes

Portions of two mitochondrial genes (12S and 16S ribosomal RNA) were sequenced to determine the phylogenetic relationships among the major clades of snakes. Thirty-six species, representing nearly all extant families, were examined and compared with sequences of a tuatara and three families of lizards. Snakes were found to constitute a monophyletic group (confidence probability [CP] = 96%), with the scolecophidians (blind snakes) as the most basal lineages (CP = 99%). This finding supports the hypothesis that snakes underwent a subterranean period early in their evolution. Caenophidians (advanced snakes), excluding Acrochordus, were found to be monophyletic (CP = 99%). Among the caenophidians, viperids were monophyletic (CP = 98%) and formed the sister group to the elapids plus colubrids (CP = 94%). Within the viperids, two monophyletic groups were identified: true vipers (CP = 98%) and pit vipers plus Azemiops (CP = 99%). The elapids plus Atractaspis formed a monophyletic clade (CP = 99%). Within the paraphyletic Colubridae, the largely Holarctic Colubrinae was found to be a monophyletic assemblage (CP = 98%), and the Xenodontinae was found to be polyphyletic (CP = 91%). Monophyly of the henophidians (primitive snakes) was neither supported nor rejected because of the weak resolution of relationships among those taxa, except for the clustering of Calabaria with a uropeltid, Rhinophis (CP = 94%).      

A nuclear DNA phylogeny and proposed taxonomic revision of African greenbuls (Aves, Passeriformes, Pycnonotidae)

The Pycnonotidae (bulbuls and greenbuls) comprise approximately 130 species and are widely distributed across Africa and Asia, mainly in evergreen thickets and forest. Recent molecular findings suggest a basal split between the African and the Asian species, although the three African Pycnonotus species are part of the Asian radiation and represent a relative recent immigration to Africa. In this study we investigate the phylogenetic relationships within the African clade, which with the exclusion of Pycnonotus contains approximately 50 species, of which the majority are placed in three large genera Andropadus , Phyllastrephus and Chlorocichla . We use three nuclear markers (myoglobin intron 2, ODC introns 6 and 7 along with intervening exon 7, and β-fibrinogen intron 5), together encompassing 2072 aligned positions, to infer the relationships within the African clade. The resulting tree is generally well supported and indicates that none of the three largest currently recognized genera are monophyletic. For instance, the species included in Andropadus represent three different clades that are not each other's closest relatives. The montane species currently placed in that genus form a strongly supported clade, which is sister to Ixonotus , Thescelocichla, Baeopogon and Chlorocichla , although within this clade the genus Chlorocichla is polyphyletic. The remaining Andropadus species fall into two groups, one of these with A . importunus and A . gracilirostris , which along with Calyptocichla serina form a basal branch in the African greenbul radiation. In support of some previous studies the Leaf-love ( Pyrrhurus scandens ) is placed within Phyllastrephus . We also propose a new classification that reflects the phylogenetic relationships among African greenbuls.     

Systematics of Amaryllidaceae based on cladistic analysis of plastid sequence data

Cladistic analyses of plastid DNA sequences rbcL and trnL-F are presented separately and combined for 48 genera of Amaryllidaceae and 29 genera of related asparagalean families. The combined analysis is the most highly resolved of the three and provides good support for the monophyly of Amaryllidaceae and indicates Agapanthaceae as its sister family. Alliaceae are in turn sister to the Amaryllidaceae/Agapanthaceae clade. The origins of the family appear to be western Gondwanaland (Africa), and infrafamilial relationships are resolved along biogeographic lines. Tribe Amaryllideae, primarily South African, is sister to the rest of Amaryllidaceae; this tribe is supported by numerous morphological synapomorphies as well. The remaining two African tribes of the family, Haemantheae and Cyrtantheae, are well supported, but their position relative to the Australasian Calostemmateae and a large clade comprising the Eurasian and American genera, is not yet clear. The Eurasian and American elements of the family are each monophyletic sister clades. Internal resolution of the Eurasian clade only partially supports currently accepted tribal concepts, and few conclusions can be drawn on the relationships of the genera based on these data. A monophyletic Lycorideae (Central and East Asian) is weakly supported. Galanthus and Leucojum (Galantheae pro parte) are supported as sister genera by the bootstrap. The American clade shows a higher degree of internal resolution. Hippeastreae (minus Griffinia and Worsleya) are well supported, and Zephyranthinae are resolved as a distinct subtribe. An Andean clade marked by a chromosome number of 2n = 46 (and derivatives thereof) is resolved with weak support. The plastid DNA phylogenies are discussed in the context of biogeography and character evolution in the family.     

Molecular phylogenetic analysis of Podostemaceae: implications for taxonomy of major groups

The river‐weed family Podostemaceae (c. 300 species in c. 54 genera) shows a number of morphological innovations to be adapted to its unusual aquatic habitat, and its unique or rare bauplan features have been reflected in the traditional (i.e. non‐molecular) classification recognizing numerous monotypic or oligospecific genera. The infrasubfamilial relationships of many genera remained unclear. The present study used molecular phylogenetic analysis of matK sequences for 657 samples (c. 132 species/c. 43 genera). The family was traditionally divided into three subfamilies (Podostemoideae, Tristichoideae and Weddellinoideae). American Podostemoideae were shown to be polyphyletic and divided into four clades, i.e. Ceratolacis, Diamantina, Podostemum and all other genera. Among the podostemoid clades, Diamantina was the first branching clade and a clade comprising Mourera and the Apinagia subclade was then sister to the remainder of the New World and Old World Podostemoideae with low statistic supports. The Old World Podostemoideae comprised four monophyletic clades, i.e. two African clades, one Madagascan clade and one Asian clade, although the relationships among these clades and American Ceratolacis and Podostemum were poorly resolved. African Podostemoideae were polyphyletic, with Saxicolella pro parte being weakly supported as sister to the remaining Old World Podostemoideae plus Ceratolacis and Podostemum. In contrast to the American and African clades, monophyly of four Asian subclades was well supported. Plants of Tristicha (Tristichoideae) and of Weddellina (Weddellinoideae), which are currently treated as monospecific, had great matK differentiation equivalent to at least interspecific variation. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 461–492.     

A molecular phylogenetic analysis of the family Rhacophoridae with an emphasis on the Asian and African genera

Using characters from mitochondrial DNA to construct maximum parsimony and maximum likelihood trees, we performed a phylogenetic analysis on representative species of 14 genera: 12 that belong to the treefrog family Rhacophoridae and two, Amolops and Rana, that are not rhacophorids. Our results support a phylogenetic hypothesis that depicts a monophyletic family Rhacophoridae. In this family, the Malagasy genera Aglyptodactylus, Boophis, Mantella, and Mantidactylus form a well-supported sister clade to all other rhacophorid genera, and Mantella is the sister taxon to Mantidactylus. Within the Asian/African genera, the genus Buergeria forms a well-supported clade of four species. The genera, except for Chirixalus, are generally monophyletic. An exception to this is that Polypedates dennysii clusters with species of Rhacophorus, suggesting that the taxonomy of the rhacophorids should be revised to reflect this relationship. Chirixalus is not monophyletic. Unexpectedly, there is strong support for Chirixalus doriae from Southeast Asia forming a clade with species of the African genus Chiromantis, suggesting that Chiromantis dispersed to Africa from Asia. Also, there is strong support for the sister taxon relationship of Chirixalus eiffingeri and Chirixalus idiootocus apart from other congeners.     

Snake relationships revealed by slow-evolving proteins: a preliminary survey

We present an initial evaluation of relationships among a diverse sample of 215 species of snakes (8% of the world snake fauna) representing nine of the 16 commonly-recognized families. Allelic variation at four slow-evolving. protein-coding loci, detected by starch-gel electrophoresis, was found to be informative for estimating relationships among these species at several levels. The numerous alleles detected at these loci [ Arp -2 (42 alleles). Ltlh -2 (43), Mdh -1 (29), Pgm (Z)] provided unexpected clarity in partitioning these taxa. Most congeneric species and several closely-related genera have the same allele at all four loci or differ at only a single locus. At thc other extreme are those species with three or four unique alleles; these taxa cannot be placed in this analysis. Species sharing two or three distinctive alleles are those most clearly separated into clades. Typhlopids, pythonids, viperids, and elapids were resolved into individual clades. whereas bods were separated into boincs and erycines, and colubrids appeared as scveral distinct clades (colubrines, natricines, psammophines, homalopsines, and xenodontines). Viperids were recognized as a major division containing three separate clades: Asian and American crotalines. Pabearctic and Oriental viperines, and Ethiopian causines. The typhlopids were found to be the basal clade, with the North American erycine boid Chrrrino and the West Indian woodsnakes Tropidophi, Y near the base. A number of species and some small clades were not allocated because of uninformative (common, unique, or conflicting) alleles. Of the 21 S species examined, five to eight appear to have been misplaced in the analysis of these electrophoretic data.     

A Simple and Novel Strategy for the Production of a Pan-specific Antiserum against Elapid Snakes of Asia

Snakebite envenomation is a serious medical problem in many tropical developing countries and was considered by WHO as a neglected tropical disease. Antivenom (AV), the rational and most effective treatment modality, is either unaffordable and/or unavailable in many affected countries. Moreover, each AV is specific to only one (monospecific) or a few (polyspecific) snake venoms. This demands that each country to prepare AV against its local snake venoms, which is often not feasible. Preparation of a ‘pan-specific’ AV against many snakes over a wide geographical area in some countries/regions has not been possible. If a ‘pan-specific’ AV effective against a variety of snakes from many countries could be prepared, it could be produced economically in large volume for use in many countries and save many lives. The aim of this study was to produce a pan-specific antiserum effective against major medically important elapids in Asia. The strategy was to use toxin fractions (TFs) of the venoms in place of crude venoms in order to reduce the number of antigens the horses were exposed to. This enabled inclusion of a greater variety of elapid venoms in the immunogen mix, thus exposing the horse immune system to a diverse repertoire of toxin epitopes, and gave rise to antiserum with wide paraspecificity against elapid venoms. Twelve venom samples from six medically important elapid snakes (4 Naja spp. and 2 Bungarus spp.) were collected from 12 regions/countries in Asia. Nine of these 12 venoms were ultra-filtered to remove high molecular weight, non-toxic and highly immunogenic proteins. The remaining 3 venoms were not ultra-filtered due to limited amounts available. The 9 toxin fractions (TFs) together with the 3 crude venoms were emulsified in complete Freund’s adjuvant and used to immunize 3 horses using a low dose, low volume, multisite immunization protocol. The horse antisera were assayed by ELISA and by in vivo lethality neutralization in mice. The findings were: a) The 9 TFs were shown to contain all of the venom toxins but were devoid of high MW proteins. When these TFs, together with the 3 crude venoms, were used as the immunogen, satisfactory ELISA antibody titers against homologous/heterologous venoms were obtained. b) The horse antiserum immunologically reacted with and neutralized the lethal effects of both the homologous and the 16 heterologous Asian/African elapid venoms tested. Thus, the use of TFs in place of crude venoms and the inclusion of a variety of elapid venoms in the immunogen mix resulted in antiserum with wide paraspecificity against elapid venoms from distant geographic areas. The antivenom prepared from this antiserum would be expected to be pan-specific and effective in treating envenomations by most elapids in many Asian countries. Due to economies of scale, the antivenom could be produced inexpensively and save many lives. This simple strategy and procedure could be readily adapted for the production of pan-specific antisera against elapids of other continents.     

Mid-Tertiary elapid snakes (Squamata, Colubroidea) from Riversleigh, northern Australia: early steps in a continent-wide adaptive radiation

Vertebral and cranial remains of elapid snakes have been collected from fossil assemblages at Riversleigh, north-west Queensland, Australia; most are Miocene but one may be late Oligocene and another as young as Pliocene. The oldest specimen (probably the oldest elapid yet known anywhere) is a vertebra that can be referred provisionally to the extant taxon Laticauda (Hydrophiinae, sensu Slowinski and Keogh, 2000), implying that the basal divergences among Australasian hydrophiine lineages had occurred by the early Miocene, in contrast to most previous estimates for the age of this geographically isolated adaptive radiation. Associated vertebrae and jaw elements from a Late Miocene deposit are described as Incongruelaps iteratus nov. gen. et sp., which has a unique combination of unusual derived characters otherwise found separately in several extant hydrophiine taxa that are only distantly related. Associated vertebrae from other sites, and two parietals from a possibly Pliocene deposit, suggest the presence of several other taxa distinct from extant forms, but the amount of material (and knowledge of variation in extant taxa) is currently insufficient to diagnose these forms. The Tertiary elapids of Riversleigh thus appear to be relatively diverse taxonomically, but low in abundance and, with one exception, not referable to extant taxa below the level of Hydrophiinae. This implies that the present diversity of hydrophiine elapids (31 recognized terrestrial genera, and approximately 16 marine) represents the result of substantial extinction as well as the “cone of increasing diversity” that could be inferred from phylogenetic studies on extant forms.     

Phylogenetic position of the southern African members of the tribe Psoraleeae based on molecular and morphological data

The tribe Psoraleeae (Leguminosae subfamily Papilionoideae) comprises 185 species in nine genera that have a nearly worldwide distribution, occurring predominantly in Mediterranean regions. About 60% of the species belong to the genera, Otholobium C.H.Stirt. and Psoralea L., which have a centre of diversity in the Cape Floristic Region of South Africa. Since previous molecular studies have sampled only a few species of the tribe from this region, this study sought to determine the phylogenetic position of the southern African genera and to test whether they are monophyletic. Phylogenetic relationships were reconstructed using DNA sequence data (trnL-F, rpoB-trnC and ITS) and seven morphological characters, which diagnose the two southern African genera. The data were analysed using the parsimony method. There was strong support for the Psoraleeae as a clade, but most of the nodes within the large genera were poorly supported. The southern African species of Psoralea and Otholobium together formed a strongly supported clade. This clade was sister to the genus Hoita Rydb., but without support. However, the Psoralea species were nested within the southern African Otholobium. Additionally, some South American species that are currently recognised as Otholobium were resolved in a clade distinct from the southern African species, making Otholobium polyphyletic. Morphological characters that separate Otholobium and Psoralea are discussed. Finally, the southern African genera as currently circumscribed are not monophyletic. However, further investigations using more informative DNA loci are required to validate this observation. Furthermore, the taxonomic placement of the South American species needs to be reviewed.     

Phylogenetic relationships of xenodontine snakes inferred from 12S and 16S ribosomal RNA sequences

The phylogenetic relationships of xenodontine snakes are inferred from sequence analyses of portions of two mitochondrial genes (12S and 16S ribosomal RNA) in 85 species. Although support values for most of the basal nodes are low, the general pattern of cladogenesis observed is congruent with many independent molecular, morphological, and geographical data. The monophyly of xenodontines and the basal position of North American xenodontines in comparison with Neotropical xenodontines are favored, suggesting an Asian-North American origin of xenodontines. West Indian xenodontines (including endemic genera and members of the genus Alsophis) appear to form a monophyletic group belonging to the South American clade. Their mid-Cenozoic origin by dispersal using ocean currents is supported. Within South American mainland xenodontines, the tribes Hydropsini, Pseudoboini, and Xenodontini are monophyletic. Finally, our results suggest that some morphological and ecological traits concerning maxillary dentition, macrohabitat use, and foraging strategy have appeared multiple times during the evolution of xenodontine snakes.     

Venom glands and some associated muscles in sea snakes

The venom glands and related muscles of sea snakes conform in their general structure to those of the terrestrial elapids. The venom gland, however, is smaller in size and the accessory gland is considerably reduced. A similar pattern is found in the Australian elapid Notechis. The musculus compressor glandulae is well developed in the sea snakes and in some species its posterior-medial portion runs uninterruptedly from the origin to the insertion of the muscle. This might be considered as a primitive condition suggesting an early divergence of the sea snakes from an ancestral elapid stock. Three species of sea snakes, Aipysurus eydouxi, Emydocephalus annulatus, and E. ijimae, feed on fish eggs and have very small, but still functioning, venom glands. The reduced accessory gland of the sea snakes is apparently connected with their aquatic environment, as a similar condition is found also in the elapine Boulengerina annulata which lives in large lakes of Central Africa. The similarity in structure of the venom gland between sea snakes and Notechis scutatus may point to a possible phylogenetic relationship between this group of Australian elapids and hydrophiine snakes.     

Fingerprint correspondence of hemoglobins and the relationships of sea snakes.

1. Peptide fingerprints of tryptic digests of the globins of sea snake species of Hydrophis, Pelamis, Aipysurus, Laticauda and the terrestrial elapid Naja were compared. 2. Globin divergence, as estimated from peptide fingerprints, paralleled closely transferrin divergence, as measured immunologically. 3. Taxonomic affinities, suggested by the fingerprint data, are concordant with McDowell's taxonomic system for sea snakes with the following exceptions: (a) Laticauda shows a closer affinity to the true sea snakes than to the terrestrial elapid Naja. (b) Sea snakes appear to be more widely divergent from terrestrial elapids than his scheme suggests.