Zbyněk Roček

Taxonomy and distribution of Tertiary discoglossids (Anura) of the genus Latonia V. Meyer,, 1843

Abstract Definition of the genus Latonia v. Meyer ,, 1843 (Anura, Discoglossidae) and description of all its known skeletalelements are given. Taxonomic revision based on both articulated skeletons and disarticulated bones from the Late Oligocene to Pliocene deposits of various European localities revealed that Prodiscoglossus vertaizoni Friant ,, 1944 is in fact the earliest known Latonia identical with that from the French locality Coderet, both of the Late Oligocene age. The Miocene representatives of the genus, namely Latonia seyfriedi v. Meyer .. 1843, L. gigantea ( Lartet ,, 1851), L. ragei Hossini ,, 1993, and Latonia sp. have been widely spread in western, central, and eastern Europe. General evolutionary trends that can be recognized in the Miocene and Pliocene material are appearance of the secondary dermal sculpture on the maxillae in some species, and gigantism. Summary of evolution within the genus Latonia and a revised description of the holotype of L. seyfriedi and all other known material from the type locality Ohningen (including a newly discovered specimen) are given. It was confirmed that Discoglossus giganteus Wettstein-Westersheimb ,, 1955 and Pelobates robustus Bolkay ,, 1913 are synonyms of Latonia,, and the same holds (besides mentioned “Prodiscoglossus” vertaizoni)) also for Diplopelturus ruscinensis Deperet ,, 1890. Latonia fejfari ( Spinar ,, 1975) and L. kolebabi Spinar ,, 1976 are synonyms of L. gigantea.. Since L. gigantea and L. ragei were described on the basis of disarticulated bones (the principal diagnostic character being presence or absence of sculpture on the maxilla), whereas L. seyfriedi was based on articulated skeletons embedded by their dorsal side in matrix, the taxonomic relations among these three forms remain unsolved until chemical preparation of the latter holotype will be possible. Available data on the geographic and stratigraphic distribution are summarized and discussed (together with structural evolution within the genus) on the background of the palaeogeographic and palaeoclimatic situation in Europe during the Neogene.

Pelvic and thigh musculature in frogs (Anura) and origin of anuran jumping locomotion

Comparative analysis of the anuran pelvic and thigh musculoskeletal system revealed that the thigh extensors, responsible for the initial phase of jump, the propulsive stroke in swimming and, if used asynchronously, also for walking, are least affected by the transformations observed between anurans and their temnospondyl ancestors (as reflected in contemporary caudates). The iliac shaft and urostyle, two of the most important anuran apomorphies, represent skeletal support for muscles that are mostly protractors of the femur or are important in attaining a crouching position, a necessary prerequisite for rapid escape. All of these muscles originate or insert on the iliac shaft. As the orientation of the pubis, ischium and ilium is the same in anurans, caudates and by inference also in their temnospondyl ancestors, it is probable that the pelvis was shifted from the sacral vertebra posteriorly along the reduced and stiffened tail (urostyle) by the elongation of the illiac shaft. Thus, the original vertical orientation of the ilium was maintained (which is also demonstrated by stable origins of the glutaeus maximus, iliofemoralis and iliofibularis on the tuber superius) and the shaft itself is a new structure. A review of functional analysis of anuran locomotion suggests some clear differences from that in caudates, suggesting that terrestrial jumping may have been a primary locomotor activity, from which other types of anuran locomotion are derived.

Development of the pelvis and posterior part of the vertebral column in the Anura

The anuran pelvic girdle is unique among all amphibians in that its acetabular portion is located far posterior to the sacrum, lateral to the postsacral (= caudal) vertebral column, which is reduced to a single rod‐like element called the urostyle. This situation in the adult is strikingly different not only from that in ancestral temnospondyls but also in other modern amphibians. Because there is no fossil that would document this evolutionary anatomical modification except for Triadobatrachus, the only data may be inferred from development in modern anurans. We chose seven anuran species (belonging to the genera Discoglossus, Bombina, Pelobates, Bufo, Rana and Xenopus), representing the principal locomotory types (saltation, swimming, crawling and burrowing). Development of the pelvic girdle was studied on cleared and stained whole mounts and partly on serial histological sections. The basic developmental pattern was similar in all species: the pelvis on both sides develops from two centres (puboischiadic and iliac, respectively). The ilium then extends vertically towards the sacral vertebra and later rotates posteriorly so that ultimately the acetabulum is lateral to the tail (= urostyle). Only minor deviations from this pattern were found, mainly associated with differences in water and terrestrial dwelling.

Mesozoic and Tertiary Anura of Laurasia

Anurans of Laurasia have a long history that begins with the earliest known anuran, Prosalirus, from the Early Jurassic of Arizona, USA. At that time, western Laurasia (North America) was still connected with Gondwana, so faunal interchange was still possible between those parts of the former Pangean supercontinent. The anuran fossil record from the Jurassic and Cretaceous of Laurasia is mainly represented by disarticulated skeletal elements similar to those of Prosalirus (e.g. amphicoelous vertebrae indicating the presence of continuous notochord; ilia without dorsal crest and dorsal tubercle; small body size). Because the morphology of the ilium, the most commonly preserved element of Mesozoic anurans, superficially recalls that of Recent Alytes, Bombina or Pelobates, Mesozoic anurans often were assigned to discoglossids and pelobatids. The Cretaceous portion of the Laurasian anuran record is marked by the appearance of procoelous and opisthocoelous vertebrae, ilia bearing a dorsal crest and dorsal tubercle (although such ilia may rarely be found as early as in the Jurassic) and larger body sizes. Cretaceous anuran assemblages include a mix of generalised taxa that are comparable to Recent basal anurans and more specialised taxa lacking clear affinities with any extant anurans. Some of these forms survived into the Paleocene, but in general anuran faunas on all Laurasian continents were markedly depleted in the Paleocene. Major groups of anurans appeared in the Eocene. The early Miocene is the interval when Eurasian and American herpetofaunas reached their peak taxonomic diversities. In the Pliocene, some extant anuran species appeared, but at the same time taxa that had been dominant throughout the Oligocene and Miocene (e.g. Eopelobates, palaeobatrachids) became extinct during this interval or during the subsequent Pleistocene glaciation. The brief biochronological synopsis presented here is followed by a systematic review of taxa with their diagnoses and published data on their stratigraphic and geographic distributions.

Anurans from the Lower Cretaceous Jehol Group of western Liaoning, China.

Background To date, the Lower Cretaceous Jehol Group of western Liaoning, China has yielded five monotypic genera of anurans, including Liaobatrachus grabaui, Callobatrachus sanyanensis, Mesophryne beipiaoensis, Dalianbatrachus mengi, and Yizhoubatrachus macilentus. However, the validity and distinctness of these taxa have been questioned. Methodology/Principal Finding We provide a comprehensive analysis of the Jehol frogs that includes a re-examination of the published taxa as well as an examination of a number of new specimens that have been collected over the past 10 years. The results show that the five previously named taxa can be referred to three species of one genus–Liaobatrachus grabaui, L. beipiaoensis comb. nov. and L. macilentus comb. nov.. The diagnosis of Liaobatrachus is revised, and a new diagnosis is provided for each species of this genus. We also establish Liaobatrachus zhaoi sp. nov., on the basis of a dozen well-preserved specimens from a new locality. This taxon is distinguished by a unique combination of characteristics, including relatively long hind limbs, a rounded rather than triangular acetabulum, and a gradually-tapering cultriform process of the parasphenoid. In addition, an unnamed frog from a higher horizon, which has narrow sacral diapophyses and particularly long legs, is different from Liaobatrachus and represents another form of anuran in the Jehol Biota. Conclusion/Significance Comparisons with other Mesozoic and extant anurans and the primary phylogenetic analysis both suggest that Liaobatrachus is a member of the anuran crown-group and forms a polytomy with leiopelmatids (Ascaphus and Leiopelma) and the remaining crown-group anurans (Lalagobatrachia).

Generic diversity and distributional dynamics of the Palaeobatrachidae (Amphibia: Anura)

A small palaeobatrachid from the Late Eocene of Kučlín, Czech Republic is described and compared with Middle Eocene palaeobatrachids from Messel, described here as Palaeobatrachus tobieni (Sanchiz 1998) comb. nov., and with Middle Eocene palaeobatrachids from Geiseltal. P. tobieni is the earliest palaeobatrachid documented by articulated skeletons. The description of the Eocene palaeobatrachids from Messel and Kučlín necessitated a revision of all palaeobatrachid genera. In order to correctly assess taxonomic variation within the Palaeobatrachidae, we studied variation in the frontoparietal, one of the most frequently preserved skeletal elements in the palaeobatrachids, in a sample of Palaeobatrachus grandipes from Bechlejovice, Czech Republic. It was found that other genera in which the frontoparietal is known (Pliobatrachus, Albionbatrachus) basically fit into the range of variation seen in Palaeobatrachus. Therefore, the differences that can be observed (e.g., sculpture in Albionbatrachus) may be interspecific in nature, rather than intergeneric. Moreover, some of the diagnostic characters of these genera are already used to diagnose the palaeobatrachid family (e.g., synsacrum in Pliobatrachus). Accordingly, it is proposed that these genera be synonymized with Palaeobatrachus, and that variations among the currently recognised genera be considered diagnostic at the species level only. The distribution of Eocene palaeobatrachids, encompassing only western and central Europe, contrasts with the distribution of palaeobatrachids in post-Eocene times. This suggests a shift in their distribution between the Late Cretaceous and Palaeocene (western Europe) and the Pliocene and Pleistocene (eastern Europe). The last palaeobatrachids were recorded from the Muchkap interglacial (621–568 Ka) in Russia. This implies that palaeobatrachids, as obligate water-dwellers, did not survive the Oka glaciation (474–425 Ka). They were probably “trapped” between a periglacial zone with temperatures below freezing in the north and a dry steppe zone in the south.

Comparative morphology of the ilium of anurans and urodeles (Lissamphibia) and a re-assessment of the anuran affinities of Nezpercius dodsoni Blob et al., 2001

ABSTRACT Ilia of anurans (frogs) and urodeles (salamanders) are commonly recovered from microvertebrate fossil localities. Ilia in these clades are distinctive when complete and articulated with the rest of the pelvic girdle, but when preserved as isolated and broken fossils they may appear superficially similar. Reliable identification of urodele ilia is further hampered by limited information about the basic structure and contacts of the bone and its variation within the clade. Here we demonstrate that the ilium is more variable among urodeles than previously realized and provide the first detailed inventory of features that are potentially useful for differentiating ilia of anurans and urodeles. Many of these features relate to differences between the two clades in the orientation of the ilium and its contacts with other bones and with soft tissues. Based on the results of our survey, we re-interpret the holotype and two referred ilia of Nezpercius dodsoni (Late Cretaceous; Montana, U.S.A.) as being from an indeterminate urodele, not an anuran as originally described. Additional examples of Late Cretaceous urodele ilia are documented to highlight some of the variation seen in fossil urodele ilia and to aid in the proper identification of such specimens.

A NEW SPECIES OF THAUMASTOSAURUS (AMPHIBIA: ANURA) FROM THE EOCENE OF EUROPE

Abstract Thaumastosaurus gezei, sp. nov., is described based on the incomplete, holotype skull and an isolated, referred squamosal, both from the so-called “old collections” (late middle or late Eocene in age) from the Phosphorites du Quercy, France. A suite of cranial features, mainly involving sculpture patterns and details of the maxilla and squamosal, differentiates T. gezei from the other three species of Thaumastosaurus. T. gezei appears to be unique among known species of Thaumastosaurus and is unusual among other anurans in having an anteriorly elongate process of the squamosal that extends along the entire dorsal edge of the maxilla, thereby preventing the maxilla from contacting the nasal and contributing to the orbital margin. This derived squamosal configuration, and some other cranial features, suggest a possible relationship between Thaumastosaurus and the South American ceratophryids. If such a relationship proves correct, Thaumastosaurus would be one of the few vertebrate taxa from the Eocene of Europe with South American affinities.

Development of the ethmoidal structures of the endocranium in the anuran Pipa pipa

Investigation of eight developmental stages by means of serial sections and subsequent graphic or wax model reconstructions, as well as by means of cleared‐and‐stained and dissected material, revealed that the ethmoidal endocranium in Pipa pipa consists in early states of a single horizontal ethmoid plate lacking labial cartilages. Later in the course of development, structures comparable with those in other anurans appear, though modified and of reduced size. These adult structures arise from the new cartilaginous tissue located above the former larval ethmoid plate, whereas the latter entirely disappear. This phenomenon can be observed also in P. carvalhoi and in Xenopus laevis; hence, it supposedly occurs in all pipids. On the other hand, in anuran larvae, which develop cornua trabecularum in the ethmoidal region, these persist in adults as part of the nasal septum. Positional and developmental differences suggest that, although the ethmoid plate and the cornua trabecularum arise from the same region of the cranial neural crest, they are not fully corresponding structures. Comparison with adults of other pipid genera confirmed the conclusion of some earlier investigators that P. pipa is the most specialized among pipids.

The Euro-American genus Eopelobates, and a re-definition of the family Pelobatidae (Amphibia, Anura)

The extinct Eopelobates (Eocene of western North America; Eocene–Pliocene of Europe) and Pelobates (Oligocene–Recent of Europe; Recent of northern Africa and the Middle East) are superficially toad-like anurans that are united within the family Pelobatidae mainly on the basis of a unique, tripartite frontoparietal complex. Both genera have a relatively good fossil record consisting of isolated bones, skeletons, and developmental series of tadpoles through adults, all of which are potentially informative for tracing the evolutionary history of the family. Eopelobates is of interest for several reasons. Of the two pelobatid genera, Eopelobates appears earlier in the fossil record (early Eocene vs. late Oligocene) and it is more primitive in lacking many of the features associated with fossoriality in extant Pelobates. The taxonomic composition of Eopelobates has been contentious and at least one putative new species has long been recognised, but never formally named. Here, we provide updated taxonomic accounts for Pelobatoidea, Pelobatidae, Pelobates, and Eopelobates and document development within a series of tadpoles and juveniles of E. bayeri from Bechlejovice (late Oligocene in age), Czech Republic. We also provide updated accounts for the five previously named and currently accepted species of Eopelobates. For the European congeners, E. anthracinus (late Oligocene) and E. bayeri (early Oligocene–middle Miocene) can confidently be regarded as separate species; although the distinction between E. hinschei and E. wagneri (both middle Eocene) is less certain, we provisionally maintain them as separate species. Micro-CT scans for the holotype skeleton of E. grandis (latest Eocene, USA) help resolve some problematic features, most notably showing that the cranial sculpture is of the pit-and-ridge style that is typical for Eopelobates. A sixth congener is named and described based on two skeletons from the middle Eocene portion of the Green River Formation, in Wyoming, USA. We caution that reports of Eopelobates-like anurans from the pre-Eocene of western North America and the early Eocene of India are based on isolated bones that cannot be assigned with confidence to that genus. The presence of Eopelobates in both North America and Europe may be explained by dispersal via the high latitude land bridge that connected those two continents during the late Paleocene through Eocene. The pelobatid fossil record is informative for documenting the nature and timing of changes in cranial features (e.g. ornament patterns, shape of nasals, pattern of frontoparietal–squamosal contact) from the inferred primitive condition seen in most Eopelobates to the more derived condition seen in extant Pelobates, but it is less informative for tracing the evolution of fossoriality, which is a key attribute of extant Pelobates.