Ben Creisler
Some recent reptile and amphibian papers:
Free pdf:
Dyrosaurids were highly specialized, largely marine, relatives of living crocodylians, and one of the few archosaur lineages to survive the K-Pg extinction. Dyrosaurids lived during the Cretaceous to the Eocene and represent a unique combination of morphology and ecology not seen in living crocodylians. Little is known about their endocranial anatomy, leaving many questions about their neurosensory adaptations unaddressed. Recently, ÂCT (micro-computed tomography) scans were made of a well-preserved skull of Rhabdognathus, a Paleocene dyrosaurid from Mali. This marks the first time the braincase and neurosensory features of a dyrosaurid have been examined using CT. We focus our attention to three specific internal structures: the cranial endocast; the inner ear; and the paratympanic sinuses. The cranial endocast of Rhabdognathus revealed novel features including a unique conformation of its paratympanic system, a prominent dorsal venous system that communicates with the external skull table, extremely enlarged tympanic vestibules that meet at the midline of the endocranium, a prominent spherical cerebrum, and elongate olfactory tracts accounting for half the total endocast length. The bizarre laterally facing lateral Eustachian foramen of dyrosaurids is now understood to be a complex fossa including both a ventrally directed lateral Eustachian foramen and a laterally directed foramen for the basioccipital diverticulum. A novel median pterygopharyngeal canal was discovered connecting the pharynx to the adductor chamber. These revelations require a reinterpretation of the associated external foramina visible on the posterior of the skull in dyrosaurids and potentially their close relatives the pholidosaurids. The olfactory tract terminates in an enlarged olfactory region possessing complex bony projectionsâa unique morphology perhaps serving to increase surface area for olfaction. The inner ear of Rhabdognathus exhibits characteristics seen in both Pelagosaurus and Gavialis. The vestibule is spherical, as in Gavialis, but is significantly expanded. The semicircular canals are enlarged but pyramidal in shape as in the thalattosuchian Pelagosaurus. The proportion of the cochlear length to total endosseous labyrinth height is roughly 0.5 in Rhabdognathus implying that the hearing capabilities resemble that of thalattosuchians. A suite of expanded sense organs (e.g., bony olfactory lamina; hypertrophied vestibule of the inner ear), and the clear expansion of the cerebrum to a more symmetrical and spherical shape suggest that dyrosaurids possess neuroanatomical modifications facilitating an agile predatory near-shore ecology.
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The discovery of cryptic biodiversity has blossomed under the advancements of genetic techniques, but species identification via morphology remains crucial to effective conservation efforts. In this study, we tested the use of continuous cranial shape variation in distinguishing the two living species of Mecistops: the West African slenderâsnouted crocodile (M. cataphractus) and the Central African slenderâsnouted crocodile (M. leptorhynchus). Using a combination of geometric morphometric characters and ratios of linear measurements, we identified statistically significant variation in cranial bone and overall skull shape of mature individuals that corroborates existing molecular and discrete morphological evidence for two distinct, extant species within Mecistops. Specifically, variation in the shape of the nasal appears particularly diagnostic, while ratios involving metrics of snout length to snout width at the premaxillary notch offer distinguishing features easily measured in the field. Because of the complementary results and applications of the morphometric and cranial ratio analyses, we argue that both methodologies remain relevant to species identification. Moreover, we recommend continued cooperation between geneticists and morphologists in diagnosing species of conservation concern.
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Free pdf:
Carla Bardua, Anne-Claire Fabre, Julien Clavel, Margot Bon, Kalpana Das, Edward L. Stanley, David C. Blackburn & Anjali Goswami (2021)
Size, microhabitat, and loss of larval feeding drive cranial diversification in frogs.
Nature Communications 12, Article number: 2503
doi:
https://doi.org/10.1038/s41467-021-22792-y https://www.nature.com/articles/s41467-021-22792-yFree pdf:
https://www.nature.com/articles/s41467-021-22792-y.pdfHabitat is one of the most important factors shaping organismal morphology, but it may vary across life history stages. Ontogenetic shifts in ecology may introduce antagonistic selection that constrains adult phenotype, particularly with ecologically distinct developmental phases such as the free-living, feeding larval stage of many frogs (Lissamphibia: Anura). We test the relative influences of developmental and ecological factors on the diversification of adult skull morphology with a detailed analysis of 15 individual cranial regions across 173 anuran species, representing every extant family. Skull size, adult microhabitat, larval feeding, and ossification timing are all significant factors shaping aspects of cranial evolution in frogs, with late-ossifying elements showing the greatest disparity and fastest evolutionary rates. Size and microhabitat show the strongest effects on cranial shape, and we identify a "large size-wide skull" pattern of anuran, and possibly amphibian, evolutionary allometry. Fossorial and aquatic microhabitats occupy distinct regions of morphospace and display fast evolution and high disparity. Taxa with and without feeding larvae do not notably differ in cranial morphology. However, loss of an actively feeding larval stage is associated with higher evolutionary rates and disparity, suggesting that functional pressures experienced earlier in ontogeny significantly impact adult morphological evolution.
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Free pdf:
Mo Li, ÂZibo Gao, ÂJili Wang, ÂWei Song, ÂQingzhu Zhang, ÂJin Tong Â& Lili Ren (2021)
Cooperation behavior of foreâ And hindlimbs during jumping in Rana dybowskii and Xenopus laevis
Ecology and Evolution (advance online publication)
doi:
https://doi.org/10.1002/ece3.7589https://onlinelibrary.wiley.com/doi/10.1002/ece3.7589Free pdf:
https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.7589Frogs are characterized by their outstanding jumping ability, depending on the rapid extension of hindlimbs to propel their bodies into air. A typical jumping cycle could be broken into four phases: preparation, takeoff, flight, and landing. Considerable research has been performed to discuss the function of hindlimbs of frogs during takeoff phase, whereas the literature of limbs' motion in jumping between different species was limited. To profile the evolution of locomotion in anurans, it is necessary to investigate on the motion of foreâ and hindlimbs of frogs within different taxa. In this work, we put forward a detailed description of jumping behavior of two frog species, Rana dybowskii and Xenopus laevis. Highâspeed cameras were used to explore the movement of different joints in foreâ and hindlimbs of these two animals, and kinematic analysis was operated to identify both homologous behaviors and significant differences between them. We found that the Rana dybowskii's foreâ and hindlimbs had good cooperation during jumping, while the Xenopus laevis' uncooperative behavior in limbs may give a functional explanation for the deficiency in terrestrial jumping; besides, the R. dybowskii's landing followed the âhandsâbellyâfeet slapâ strategy, and Xenopus laevis had clumsy landing with âbellyâflopsâ sequence. The result gained here clarifies the cooperation behavior of anuran limbs and may supply a new insight into our understanding of the anuran's evolution.
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Free pdf:
Cladistic datasets of morphological characters are comprised of observations that exhibit varying degrees of consistency with underlying phylogenetic hypotheses, reflecting the acquisition and retention of character states (highly consistent characters), or the convergent evolution and loss of character states (less consistent characters). The consistency between phylogenetic history and individual character histories has a bearing both on the evolutionary process and on the relative ease with which phylogenetic history may be inferred from morphological data. We surveyed 486 tetrapod morphological cladistic datasets to establish an empirical distribution of consistency among characters and datasets. Average dataset size has increased in the number of characters and taxa through time. The Consistency Index measure of homoplasy decreases as more characters are added but the most significant decreases result from the addition of taxa. Retention Index and Homoplasy Excess Ratio remain relatively constant with changes in taxa and character number. Our sampling of larger datasets confirms that the positive relationship between dataset size and homoplasy is primarily caused by an increase in taxa, not an increase in characters. Genealogies of cladistic data matrices for early vertebrates, scalidophorans and crocodilians, which have been modified in succession, show a trend of generally consistent quality through research time. Thus, we find no support for the widely shared conjecture that in the search for phylogenetic resolution, high quality phylogenetic characters are quickly exhausted, with subsequent research leading to the inclusion of potentially misleading characters exhibiting high levels of homoplasy.
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New issue of Bulletin of Zoological Nomenclature
Raymond Hoser "taxonomic vandalism" --ICZN declines to act
The International Commission on Zoological Nomenclature finds no basis under the provisions of the Code for regarding the name Spracklandus as unavailable, nor for regarding any of issues 1â24 of Australasian Journal of Herpetology as being unpublished in the sense of the Code, but the Commission has declined to use its powers to confirm what is obvious. The Commission is not empowered to take Appendix A of the Code (Code of Ethics) into account in its rulings on this or any other Case.
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Free pdf:
In times of increasing easiness to produce publications, attempts have been made to use the Code's requirements for publication to declare controversial works unavailable. I advise against such strategy, because in this day and age, these requirements are very easily met by anybody and their violation very difficult to prove. This is illustrated by one example each from herpetology, ichthyology, and entomology. Contemporary works with controversial taxonomy and available nomenclatural acts are better taken care of by the scientific community and resolved in the long term by prevailing usage rather than trying to declare them unavailable or seeking suppression of such works by the ICZN.
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Also:
Christer ErsÃus, Patrick Martin, Svante Martinsson & Tarmo Timm (2021)
Case 3826 â Propappus Michaelsen, 1905 and Propappidae Coates, 1986 (Annelida, Clitellata): proposed conservation by suppression of Propappus Seeley, 1888 (Vertebrata, Reptilia)
The Bulletin of Zoological Nomenclature 78(1): 17-25
doi:
https://doi.org/10.21805/bzn.v78.a006https://bioone.org/journals/the-bulletin-of-zoological-nomenclature/volume-78/issue-1/bzn.v78.a006/Case-3826--Propappus-Michaelsen-1905-and-Propappidae-Coates-1986/10.21805/bzn.v78.a006.fullThe purpose of this application, under Article 23.9.3 of the Code, is to conserve the well-used names Propappus Michaelsen, 1905 and Propappidae Coates, 1986 (Annelida) by suppression of the senior homonym Propappus Seeley, 1888 (Reptilia), a junior subjective synonym of Pareiasaurus Owen, 1876.
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