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An Extremely Peramorphic Newt (Urodela: Salamandridae: Pleurodelini) from the Latest Oligocene of Germany, and a New Phylogenetic Analysis of Extant and Extinct Salamandrids.

Marjanović D, Witzmann F - PLoS ONE (2015)

Bottom Line: Referral to a species would require a revision of the genus, but the specimen likely does not belong to the type species.The Miocene "Triturus" roehrsi is found neither with the extant Ommatotriton nor with Lissotriton, but inside an Asian/aquatic clade or, when geographic distribution is included as a character, as the sister-group to all other European molgins.The main cause for discrepancies between the results and the molecular consensus is not heterochrony, but adaptations to a life in mountain streams; this is the most likely reason why the Paleocene Koalliella from western Europe forms the sister-group to some or all of the most aquatic extant newts in different analyses.

View Article: PubMed Central - PubMed

Affiliation: Museum für Naturkunde, Leibniz Institute for Evolutionary and Biodiversity Research, Humboldt University, Berlin, Germany.

ABSTRACT
We describe an Oligocene newt specimen from western Germany that has gone practically unnoticed in the literature despite having been housed in the Museum für Naturkunde (Berlin) for a century. It is referable to the coeval Chelotriton, but is unusually peramorphic; for many characters it is more peramorphic than all other caudates or even all other lissamphibians. Most noticeable are the position of the jaw joints far caudal to the occiput, the honeycombed sculpture on the maxilla, and the possible presence of a septomaxilla (which would be unique among salamandrids). Referral to a species would require a revision of the genus, but the specimen likely does not belong to the type species. A phylogenetic analysis of nonmolecular characters of Salamandridae, far larger than all predecessors, confirms the referral to Chelotriton. It further loosely associates the Oligocene Archaeotriton and the Miocene Carpathotriton with the extant Lissotriton, though the former may alternatively lie outside Pleurodelinae altogether. The Miocene? I. randeckensis may not belong to the extant Ichthyosaura. The Miocene "Triturus" roehrsi is found neither with the extant Ommatotriton nor with Lissotriton, but inside an Asian/aquatic clade or, when geographic distribution is included as a character, as the sister-group to all other European molgins. The main cause for discrepancies between the results and the molecular consensus is not heterochrony, but adaptations to a life in mountain streams; this is the most likely reason why the Paleocene Koalliella from western Europe forms the sister-group to some or all of the most aquatic extant newts in different analyses. We would like to urge neontologists working on salamandrids to pay renewed attention to the skeleton, not limited to the skull, as a source of diagnostic and phylogenetically informative characters.

No MeSH data available.


Related in: MedlinePlus

Strict consensus of Figs 1 and 2, reduced to the taxa they both share.This tree was used as a backbone constraint in our constrained analysis. Note the absence of Dicamptodon and of all species of Lissotriton except one, following [1]. Colors as in Fig 1.
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pone.0137068.g003: Strict consensus of Figs 1 and 2, reduced to the taxa they both share.This tree was used as a backbone constraint in our constrained analysis. Note the absence of Dicamptodon and of all species of Lissotriton except one, following [1]. Colors as in Fig 1.

Mentions: Salamandridae is an extant clade of caudates that is widely distributed in the northern hemisphere and can be found in Asia, Europe and North America, as well as the northern fringe of Africa [1]. The group is traditionally divided into the “true salamanders” (Salamandrinae), which are mostly terrestrial, and the generally more aquatic newts (Pleurodelinae); the terrestrial Salamandrina forms a third clade [1–3] (Figs 1–3) that is sometimes called Salamandrininae and appears to form the sister-group to the clade formed by Salamandrinae and Pleurodelinae together ([1]; weakly supported by [2]). The oldest known fossil salamandrid is Koalliella genzeli Herre, 1950, a likely crown- or stem-pleurodeline known from a few isolated vertebrae from the late Paleocene of Germany and France ([3–7]; all specimens lost according to [4]). The lack of older fossils, or of any stem-salamandrids, has made it difficult to estimate the time of origin of the salamandrid crown. The molecular divergence dating analysis in [1] put the 95% confidence interval at approximately 73 to 86 Ma ago when the program MultiDivTime was used and at approximately 58 to 83 Ma ago when BEAST was used instead, while the very simple method used in appendix S5 of [2] on its enormous dataset yielded an age of 75.26 Ma without error margins; the paleontological method of [7] yielded broadly compatible but poorly constrained ages (68.2 Ma according to fig 2 of [7]). In the analyses cited above, Pleurodelinae was found to consist of a clade comprising (Pleurodeles + (Tylototriton + Echinotriton)), referred to as Pleurodelini or as “primitive newts” [1], and its sister-group which contains the remaining newts (Molgini, after Molge, a junior synonym of Triturus). Pleurodelini is characterized by an overall high degree of ossification, strongly sculptured skulls with a complete frontosquamosal arch (or bar or bridge) separating the orbitotemporal fenestra from the postorbital opening, and tubercular processes on the ribs located internal to toxic skin glands; Tylototriton and Echinotriton additionally possess sculptured spine tables on the tips of their neural spines [4,5,8,9], a trait that also occurs (in less extreme form) in certain molgins. There is a number of Eocene to Pliocene salamandrids from Europe that show a similar morphology and degree of ossification of the skeleton and that are often thought to belong to Pleurodelini. These comprise fossil representatives of Pleurodeles sp. from the Miocene/Pliocene of the Iberian Peninsula and North Africa [4], Palaeopleurodeles hauffi Herre, 1941, from the Oligocene of Germany [10,11], Brachycormus noachicus (Goldfuss, 1831) from the late Oligocene of Germany [3,4,12–15] and the Eocene to Pliocene genus Chelotriton. Extant pleurodelins and the abovementioned fossil forms have been referred to as “Group II” salamandrids [4,16] and as the “Pleurodeles-Tylototriton Clade” [5], although a phylogenetic analysis incorporating all these forms has so far not been carried out.


An Extremely Peramorphic Newt (Urodela: Salamandridae: Pleurodelini) from the Latest Oligocene of Germany, and a New Phylogenetic Analysis of Extant and Extinct Salamandrids.

Marjanović D, Witzmann F - PLoS ONE (2015)

Strict consensus of Figs 1 and 2, reduced to the taxa they both share.This tree was used as a backbone constraint in our constrained analysis. Note the absence of Dicamptodon and of all species of Lissotriton except one, following [1]. Colors as in Fig 1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4589347&req=5

pone.0137068.g003: Strict consensus of Figs 1 and 2, reduced to the taxa they both share.This tree was used as a backbone constraint in our constrained analysis. Note the absence of Dicamptodon and of all species of Lissotriton except one, following [1]. Colors as in Fig 1.
Mentions: Salamandridae is an extant clade of caudates that is widely distributed in the northern hemisphere and can be found in Asia, Europe and North America, as well as the northern fringe of Africa [1]. The group is traditionally divided into the “true salamanders” (Salamandrinae), which are mostly terrestrial, and the generally more aquatic newts (Pleurodelinae); the terrestrial Salamandrina forms a third clade [1–3] (Figs 1–3) that is sometimes called Salamandrininae and appears to form the sister-group to the clade formed by Salamandrinae and Pleurodelinae together ([1]; weakly supported by [2]). The oldest known fossil salamandrid is Koalliella genzeli Herre, 1950, a likely crown- or stem-pleurodeline known from a few isolated vertebrae from the late Paleocene of Germany and France ([3–7]; all specimens lost according to [4]). The lack of older fossils, or of any stem-salamandrids, has made it difficult to estimate the time of origin of the salamandrid crown. The molecular divergence dating analysis in [1] put the 95% confidence interval at approximately 73 to 86 Ma ago when the program MultiDivTime was used and at approximately 58 to 83 Ma ago when BEAST was used instead, while the very simple method used in appendix S5 of [2] on its enormous dataset yielded an age of 75.26 Ma without error margins; the paleontological method of [7] yielded broadly compatible but poorly constrained ages (68.2 Ma according to fig 2 of [7]). In the analyses cited above, Pleurodelinae was found to consist of a clade comprising (Pleurodeles + (Tylototriton + Echinotriton)), referred to as Pleurodelini or as “primitive newts” [1], and its sister-group which contains the remaining newts (Molgini, after Molge, a junior synonym of Triturus). Pleurodelini is characterized by an overall high degree of ossification, strongly sculptured skulls with a complete frontosquamosal arch (or bar or bridge) separating the orbitotemporal fenestra from the postorbital opening, and tubercular processes on the ribs located internal to toxic skin glands; Tylototriton and Echinotriton additionally possess sculptured spine tables on the tips of their neural spines [4,5,8,9], a trait that also occurs (in less extreme form) in certain molgins. There is a number of Eocene to Pliocene salamandrids from Europe that show a similar morphology and degree of ossification of the skeleton and that are often thought to belong to Pleurodelini. These comprise fossil representatives of Pleurodeles sp. from the Miocene/Pliocene of the Iberian Peninsula and North Africa [4], Palaeopleurodeles hauffi Herre, 1941, from the Oligocene of Germany [10,11], Brachycormus noachicus (Goldfuss, 1831) from the late Oligocene of Germany [3,4,12–15] and the Eocene to Pliocene genus Chelotriton. Extant pleurodelins and the abovementioned fossil forms have been referred to as “Group II” salamandrids [4,16] and as the “Pleurodeles-Tylototriton Clade” [5], although a phylogenetic analysis incorporating all these forms has so far not been carried out.

Bottom Line: Referral to a species would require a revision of the genus, but the specimen likely does not belong to the type species.The Miocene "Triturus" roehrsi is found neither with the extant Ommatotriton nor with Lissotriton, but inside an Asian/aquatic clade or, when geographic distribution is included as a character, as the sister-group to all other European molgins.The main cause for discrepancies between the results and the molecular consensus is not heterochrony, but adaptations to a life in mountain streams; this is the most likely reason why the Paleocene Koalliella from western Europe forms the sister-group to some or all of the most aquatic extant newts in different analyses.

View Article: PubMed Central - PubMed

Affiliation: Museum für Naturkunde, Leibniz Institute for Evolutionary and Biodiversity Research, Humboldt University, Berlin, Germany.

ABSTRACT
We describe an Oligocene newt specimen from western Germany that has gone practically unnoticed in the literature despite having been housed in the Museum für Naturkunde (Berlin) for a century. It is referable to the coeval Chelotriton, but is unusually peramorphic; for many characters it is more peramorphic than all other caudates or even all other lissamphibians. Most noticeable are the position of the jaw joints far caudal to the occiput, the honeycombed sculpture on the maxilla, and the possible presence of a septomaxilla (which would be unique among salamandrids). Referral to a species would require a revision of the genus, but the specimen likely does not belong to the type species. A phylogenetic analysis of nonmolecular characters of Salamandridae, far larger than all predecessors, confirms the referral to Chelotriton. It further loosely associates the Oligocene Archaeotriton and the Miocene Carpathotriton with the extant Lissotriton, though the former may alternatively lie outside Pleurodelinae altogether. The Miocene? I. randeckensis may not belong to the extant Ichthyosaura. The Miocene "Triturus" roehrsi is found neither with the extant Ommatotriton nor with Lissotriton, but inside an Asian/aquatic clade or, when geographic distribution is included as a character, as the sister-group to all other European molgins. The main cause for discrepancies between the results and the molecular consensus is not heterochrony, but adaptations to a life in mountain streams; this is the most likely reason why the Paleocene Koalliella from western Europe forms the sister-group to some or all of the most aquatic extant newts in different analyses. We would like to urge neontologists working on salamandrids to pay renewed attention to the skeleton, not limited to the skull, as a source of diagnostic and phylogenetically informative characters.

No MeSH data available.


Related in: MedlinePlus