Limits...
Biogeography and taxonomy of extinct and endangered monk seals illuminated by ancient DNA and skull morphology.

Scheel DM, Slater GJ, Kolokotronis SO, Potter CW, Rotstein DS, Tsangaras K, Greenwood AD, Helgen KM - Zookeys (2014)

Bottom Line: Molecular, morphological and temporal divergence between the Mediterranean and "New World monk seals" (Hawaiian and Caribbean) is profound, equivalent to or greater than between sister genera of phocids.As a result, we classify the Caribbean and Hawaiian monk seals together in a newly erected genus, Neomonachus.The two genera of extant monk seals (Monachus and Neomonachus) represent old evolutionary lineages each represented by a single critically endangered species, both warranting continuing and concerted conservation attention and investment if they are to avoid the fate of their Caribbean relative.

View Article: PubMed Central - HTML - PubMed

Affiliation: Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany.

ABSTRACT
Extinctions and declines of large marine vertebrates have major ecological impacts and are of critical concern in marine environments. The Caribbean monk seal, Monachus tropicalis, last definitively reported in 1952, was one of the few marine mammal species to become extinct in historical times. Despite its importance for understanding the evolutionary biogeography of southern phocids, the relationships of M. tropicalis to the two living species of critically endangered monk seals have not been resolved. In this study we present the first molecular data for M. tropicalis, derived from museum skins. Phylogenetic analysis of cytochrome b sequences indicates that M. tropicalis was more closely related to the Hawaiian rather than the Mediterranean monk seal. Divergence time estimation implicates the formation of the Panamanian Isthmus in the speciation of Caribbean and Hawaiian monk seals. Molecular, morphological and temporal divergence between the Mediterranean and "New World monk seals" (Hawaiian and Caribbean) is profound, equivalent to or greater than between sister genera of phocids. As a result, we classify the Caribbean and Hawaiian monk seals together in a newly erected genus, Neomonachus. The two genera of extant monk seals (Monachus and Neomonachus) represent old evolutionary lineages each represented by a single critically endangered species, both warranting continuing and concerted conservation attention and investment if they are to avoid the fate of their Caribbean relative.

No MeSH data available.


Related in: MedlinePlus

Posteroventral view of the basicranium and left bulla in aMonachus monachusbNeomonachus schauinslandi, and cNeomonachus tropicalis. The bulla of Monachus is bordered posteriorly by a ventrally expanded posterior portion of the petro-mastoid complex. The petrosal abuts the bulla’s posterior wall and in ventral view forms the entire lateral and anterolateral border of the posterior lacerate foramen. In Neomonachus, the posterior part of the petrosal is visible in the posterior lacerate foramen but remains superior to the bulla. In ventral view, this gives the impression that the anterior border of the posterior lacerate foramen is formed entirely by the bulla. The posterior carotid canal opens posteroventrally in Monachus. This apparently results from a relatively complete “ring-like” opening, formed by the bulla. This form of opening is apparent in subadult and juvenile Monachus, suggesting that it is not dependent on ontogenetic development or the robusticity of the Monachus cranium relative to Neomonachus. In contrast, the posterior carotid canal of Neomonachus opens directly posteriorly, the opening being an incomplete ring and the dorsal border formed by a flattening of the bulla, perhaps resulting from the bulla’s extension over the petrosal.
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Figure 9: Posteroventral view of the basicranium and left bulla in aMonachus monachusbNeomonachus schauinslandi, and cNeomonachus tropicalis. The bulla of Monachus is bordered posteriorly by a ventrally expanded posterior portion of the petro-mastoid complex. The petrosal abuts the bulla’s posterior wall and in ventral view forms the entire lateral and anterolateral border of the posterior lacerate foramen. In Neomonachus, the posterior part of the petrosal is visible in the posterior lacerate foramen but remains superior to the bulla. In ventral view, this gives the impression that the anterior border of the posterior lacerate foramen is formed entirely by the bulla. The posterior carotid canal opens posteroventrally in Monachus. This apparently results from a relatively complete “ring-like” opening, formed by the bulla. This form of opening is apparent in subadult and juvenile Monachus, suggesting that it is not dependent on ontogenetic development or the robusticity of the Monachus cranium relative to Neomonachus. In contrast, the posterior carotid canal of Neomonachus opens directly posteriorly, the opening being an incomplete ring and the dorsal border formed by a flattening of the bulla, perhaps resulting from the bulla’s extension over the petrosal.

Mentions: In ventral view, the morphology of the petromastoid (petrosal-mastoid) complex in relation to the auditory bulla in Neomonachus is diagnostic in comparison to Monachus. King (1966) noted that having the petrosal visible within the posterior lacerate foramen was a feature that united Monachus and the phocines, although Ray (1976b) pointed out that it is difficult to distinguish the boundaries of the petrosal and mastoid (petromastoid complex) in the posterior lacerate foramen and that this character was far more variable within lobodontines than King had estimated. He argued that a better standard for delineating this character state uniting Mirounga and the lobodontines is a bulla in near contact or complete contact with the exoccipital. We agree with Ray’s assessment, but we note that the configuration of the petromastoid complex and bulla with respect to the posterior lacerate foramen is more complex within “Monachus” (i.e. sensu lato) than has been previously described. In particular, the petromastoid of Monachus monachus is clearly ventrally inflated, such that it protrudes below the rim of the posterior lacerate foramen, forming its entire lateral border (Figure 9a). Furthermore, the ventral expansion of the petromastoid almost completely excludes the flat posterior edge of the bulla from the anterior margin of the posterior lacerate foramen. This morphology, which is also present in the fossil taxon Pliophoca, has been proposed as synapormorphic for Monachini (Amson and de Muizon 2013). However, in Neomonachus, the tapering posterior margin of the bulla lies completely ventral to the petromastoid, the posterior border of which is visible within the neurocranium through the posterior lacerate foramen (Figure 9: b and c). Ray also noted that the posterior carotid foramen opens in full view in Monachus (sensu lato) but is partially concealed on the medial bulla wall in phocines (Ray 1976b). Our observations show that, for Neomonachus, the posterior carotid canal opens directly posteriorly, with a flattened dorsal roof formed by excavation of the caudal entotympanic (Figure 9). In Monachus, the canal opens postero-ventrally due to a more complete, ring-like opening. These character-state differences are clearly developed even in juvenile individuals, indicating that they are not the outcome of ontogenetic variation.


Biogeography and taxonomy of extinct and endangered monk seals illuminated by ancient DNA and skull morphology.

Scheel DM, Slater GJ, Kolokotronis SO, Potter CW, Rotstein DS, Tsangaras K, Greenwood AD, Helgen KM - Zookeys (2014)

Posteroventral view of the basicranium and left bulla in aMonachus monachusbNeomonachus schauinslandi, and cNeomonachus tropicalis. The bulla of Monachus is bordered posteriorly by a ventrally expanded posterior portion of the petro-mastoid complex. The petrosal abuts the bulla’s posterior wall and in ventral view forms the entire lateral and anterolateral border of the posterior lacerate foramen. In Neomonachus, the posterior part of the petrosal is visible in the posterior lacerate foramen but remains superior to the bulla. In ventral view, this gives the impression that the anterior border of the posterior lacerate foramen is formed entirely by the bulla. The posterior carotid canal opens posteroventrally in Monachus. This apparently results from a relatively complete “ring-like” opening, formed by the bulla. This form of opening is apparent in subadult and juvenile Monachus, suggesting that it is not dependent on ontogenetic development or the robusticity of the Monachus cranium relative to Neomonachus. In contrast, the posterior carotid canal of Neomonachus opens directly posteriorly, the opening being an incomplete ring and the dorsal border formed by a flattening of the bulla, perhaps resulting from the bulla’s extension over the petrosal.
© Copyright Policy - creative-commons-attribution
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4042687&req=5

Figure 9: Posteroventral view of the basicranium and left bulla in aMonachus monachusbNeomonachus schauinslandi, and cNeomonachus tropicalis. The bulla of Monachus is bordered posteriorly by a ventrally expanded posterior portion of the petro-mastoid complex. The petrosal abuts the bulla’s posterior wall and in ventral view forms the entire lateral and anterolateral border of the posterior lacerate foramen. In Neomonachus, the posterior part of the petrosal is visible in the posterior lacerate foramen but remains superior to the bulla. In ventral view, this gives the impression that the anterior border of the posterior lacerate foramen is formed entirely by the bulla. The posterior carotid canal opens posteroventrally in Monachus. This apparently results from a relatively complete “ring-like” opening, formed by the bulla. This form of opening is apparent in subadult and juvenile Monachus, suggesting that it is not dependent on ontogenetic development or the robusticity of the Monachus cranium relative to Neomonachus. In contrast, the posterior carotid canal of Neomonachus opens directly posteriorly, the opening being an incomplete ring and the dorsal border formed by a flattening of the bulla, perhaps resulting from the bulla’s extension over the petrosal.
Mentions: In ventral view, the morphology of the petromastoid (petrosal-mastoid) complex in relation to the auditory bulla in Neomonachus is diagnostic in comparison to Monachus. King (1966) noted that having the petrosal visible within the posterior lacerate foramen was a feature that united Monachus and the phocines, although Ray (1976b) pointed out that it is difficult to distinguish the boundaries of the petrosal and mastoid (petromastoid complex) in the posterior lacerate foramen and that this character was far more variable within lobodontines than King had estimated. He argued that a better standard for delineating this character state uniting Mirounga and the lobodontines is a bulla in near contact or complete contact with the exoccipital. We agree with Ray’s assessment, but we note that the configuration of the petromastoid complex and bulla with respect to the posterior lacerate foramen is more complex within “Monachus” (i.e. sensu lato) than has been previously described. In particular, the petromastoid of Monachus monachus is clearly ventrally inflated, such that it protrudes below the rim of the posterior lacerate foramen, forming its entire lateral border (Figure 9a). Furthermore, the ventral expansion of the petromastoid almost completely excludes the flat posterior edge of the bulla from the anterior margin of the posterior lacerate foramen. This morphology, which is also present in the fossil taxon Pliophoca, has been proposed as synapormorphic for Monachini (Amson and de Muizon 2013). However, in Neomonachus, the tapering posterior margin of the bulla lies completely ventral to the petromastoid, the posterior border of which is visible within the neurocranium through the posterior lacerate foramen (Figure 9: b and c). Ray also noted that the posterior carotid foramen opens in full view in Monachus (sensu lato) but is partially concealed on the medial bulla wall in phocines (Ray 1976b). Our observations show that, for Neomonachus, the posterior carotid canal opens directly posteriorly, with a flattened dorsal roof formed by excavation of the caudal entotympanic (Figure 9). In Monachus, the canal opens postero-ventrally due to a more complete, ring-like opening. These character-state differences are clearly developed even in juvenile individuals, indicating that they are not the outcome of ontogenetic variation.

Bottom Line: Molecular, morphological and temporal divergence between the Mediterranean and "New World monk seals" (Hawaiian and Caribbean) is profound, equivalent to or greater than between sister genera of phocids.As a result, we classify the Caribbean and Hawaiian monk seals together in a newly erected genus, Neomonachus.The two genera of extant monk seals (Monachus and Neomonachus) represent old evolutionary lineages each represented by a single critically endangered species, both warranting continuing and concerted conservation attention and investment if they are to avoid the fate of their Caribbean relative.

View Article: PubMed Central - HTML - PubMed

Affiliation: Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany.

ABSTRACT
Extinctions and declines of large marine vertebrates have major ecological impacts and are of critical concern in marine environments. The Caribbean monk seal, Monachus tropicalis, last definitively reported in 1952, was one of the few marine mammal species to become extinct in historical times. Despite its importance for understanding the evolutionary biogeography of southern phocids, the relationships of M. tropicalis to the two living species of critically endangered monk seals have not been resolved. In this study we present the first molecular data for M. tropicalis, derived from museum skins. Phylogenetic analysis of cytochrome b sequences indicates that M. tropicalis was more closely related to the Hawaiian rather than the Mediterranean monk seal. Divergence time estimation implicates the formation of the Panamanian Isthmus in the speciation of Caribbean and Hawaiian monk seals. Molecular, morphological and temporal divergence between the Mediterranean and "New World monk seals" (Hawaiian and Caribbean) is profound, equivalent to or greater than between sister genera of phocids. As a result, we classify the Caribbean and Hawaiian monk seals together in a newly erected genus, Neomonachus. The two genera of extant monk seals (Monachus and Neomonachus) represent old evolutionary lineages each represented by a single critically endangered species, both warranting continuing and concerted conservation attention and investment if they are to avoid the fate of their Caribbean relative.

No MeSH data available.


Related in: MedlinePlus