Cranial shape variation in jacarean caimanines (Crocodylia, Alligatoroidea) and its implications in the taxonomic status of extinct species: The case ofMelanosuchus fisheri

Abstract Morphological variation among the viviparous sea snakes (Hydrophiinae), a clade of fully aquatic elapid snakes, includes an extreme “microcephalic” ecomorph that has a very small head atop a narrow forebody, while the hind body is much thicker (up to three times the forebody girth). Previous research has demonstrated that this morphology has evolved at least nine times as a consequence of dietary specialization on burrowing eels, and has also examined morphological changes to the vertebral column underlying this body shape. The question addressed in this study is what happens to the skull during this extreme evolutionary change? Here we use X-ray micro-computed tomography and geometric morphometric methods to characterize cranial shape variation in 30 species of sea snakes. We investigate ontogenetic and evolutionary patterns of cranial shape diversity to understand whether cranial shape is predicted by dietary specialization, and examine whether cranial shape of microcephalic species may be a result of heterochronic processes. We show that the diminutive cranial size of microcephalic species has a convergent shape that is correlated with trophic specialization to burrowing prey. Furthermore, their cranial shape is predictable for their size and very similar to that of juvenile individuals of closely related but non-microcephalic sea snakes. Our findings suggest that heterochronic changes (resulting in pedomorphosis) have driven cranial shape convergence in response to dietary specializations in sea snakes.

Download Full-text

A three-dimensional geometric morphometrics view of the cranial shape variation and population history in the New World

American Journal of Human Biology ◽

10.1002/ajhb.22845 ◽

2016 ◽

Vol 28 (5) ◽

pp. 646-661 ◽

Cited By ~ 16

Author(s):

Manon Galland ◽

Martin Friess

Keyword(s):

Geometric Morphometrics ◽

New World ◽

Three Dimensional ◽

Population History ◽

Shape Variation ◽

Cranial Shape

Download Full-text

DNA barcodes combined with geometric morphometry challenge species hypothesis in palaemonid shrimp

ARPHA Conference Abstracts ◽

10.3897/aca.4.e65363 ◽

2021 ◽

Vol 4 ◽

Author(s):

Aleksandra Jablonska ◽

Nicolas Navarro ◽

Remi Laffont ◽

Remi Wattier ◽

Vladimir Pesic ◽

...

Keyword(s):

Taxonomic Status ◽

Balkan Peninsula ◽

Integrative Approach ◽

Shape Variation ◽

Separate Species ◽

Geometric Morphometric ◽

The Balkans ◽

Operational Taxonomic Units ◽

Freshwater Shrimps ◽

Coi Sequences

Although the Mediterranean Region is known as a hotspot for biodiversity and endemism its freshwater fauna is still greatly unexplored, and even the emblematic taxa such as decapods require in-depth integrative investigation. In our research we used integrative approach composed of various geometric morphometric and molecular methods to challenge the taxonomic status of two freshwater shrimps representing Palaemonidae: Palaemon antennarius and Palaemon minos. Basing on 352 COI sequences, three Molecular Operational Taxonomic Units (MOTUs) were defined. Two of them belonged to P. antennarius: first inhabiting Apennine Peninsula and Sicily, the second one from the Balkan Peninsula. The third MOTU corresponded to Palaemon minos from Crete. The Balkan MOTU of P. antennarius was closer to P. minos in terms of genetics, than to the other conspecific MOTU. The carapace shape variation, studied on 180 individuals, was mainly explained by the geographic distribution. Balkan and Cretan groups were clearly distinguished, while other samples were distributed along the shape gradient from Sicily and southern Apennine Peninsula to the Balkans. The results of our study showed that, either the MOTU assigned to the Apennine Peninsula and Sicily constitutes a separate species or, alternatively, P. minos should be synonymised with P. antennarius.

Download Full-text

Evolutionary morphology of the rabbit skull

PeerJ ◽

10.7717/peerj.2453 ◽

2016 ◽

Vol 4 ◽

pp. e2453 ◽

Cited By ~ 5

Author(s):

Brian Kraatz ◽

Emma Sherratt

Keyword(s):

Small Proportion ◽

Phylogenetic Signal ◽

Morphological Data ◽

Shape Variation ◽

Evolutionary Morphology ◽

Crown Group ◽

Size Change ◽

Generalist Species ◽

Facial Region ◽

Cranial Shape

The skull of leporids (rabbits and hares) is highly transformed, typified by pronounced arching of the dorsal skull and ventral flexion of the facial region (i.e., facial tilt). Previous studies show that locomotor behavior influences aspects of cranial shape in leporids, and here we use an extensive 3D geometric morphometrics dataset to further explore what influences leporid cranial diversity. Facial tilt angle, a trait that strongly correlates with locomotor mode, significantly predicts the cranial shape variation captured by the primary axis of cranial shape space, and describes a small proportion (13.2%) of overall cranial shape variation in the clade. However, locomotor mode does not correlate with overall cranial shape variation in the clade, because there are two district morphologies of generalist species, and saltators and cursorial species have similar morphologies. Cranial shape changes due to phyletic size change (evolutionary allometry) also describes a small proportion (12.5%) of cranial shape variation in the clade, but this is largely driven by the smallest living leporid, the pygmy rabbit (Brachylagus idahoensis). By integrating phylogenetic history with our geometric morphometric data, we show that the leporid cranium exhibits weak phylogenetic signal and substantial homoplasy. Though these results make it difficult to reconstruct what the ‘ancestral’ leporid skull looked like, the fossil records suggest that dorsal arching and facial tilt could have occurred before the origin of the crown group. Lastly, our study highlights the diversity of cranial variation in crown leporids, and highlights a need for additional phylogenetic work that includes stem (fossil) leporids and includes morphological data that captures the transformed morphology of rabbits and hares.

Download Full-text

Trichomycterus venulosus (Steindachner, 1915), a junior synonym of Eremophilus mutisii Humboldt, 1805 (Siluriformes: Trichomycteridae) and not an extinct species

Neotropical Ichthyology ◽

10.1590/1982-0224-20130236 ◽

2014 ◽

Vol 12 (4) ◽

pp. 707-715 ◽

Cited By ~ 6

Author(s):

Carlos DoNascimiento ◽

Saúl Prada-Pedreros ◽

Jürgen Guerrero-Kommritz

Keyword(s):

Taxonomic Status ◽

Junior Synonym ◽

Nominal Species ◽

Extinct Species ◽

Eastern Cordillera

Reexamination of the syntypes of the enigmatic Trichomycterus venulosus, described from Páramo de Cruz Verde, Eastern Cordillera of Colombia, allowed us to assess its actual taxonomic status. This nominal species is demonstrated to constitute a junior synonym of Eremophilus mutisii, and then not represents a case of extinction of a fish endemic to Colombia, as currently accepted.

Download Full-text