Ben Creisler
The new 2024 open access special issue Fossil Record 27(3) is on the topic:
The fish-to-tetrapod transition and the conquest of land by vertebrates
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Michel Laurin (2024)
Habitat of early stegocephalians (Chordata, Vertebrata, Sarcopterygii): a little saltier than most paleontologists like?
In: Witzmann F, Ruta M, Fröbisch N (Eds) The fish-to-tetrapod transition and the conquest of land by vertebrates .
Fossil Record 27(3): 299-232
doi:
https://doi.org/10.3897/fr.27.e123291https://fr.pensoft.net/article/123291/A controversy on the degree of marine influence in the paleoenvironments represented by many Paleozoic stegocephalian-bearing fossiliferous localities has persisted for decades. Many authors have equated the absence of a typical stenohaline marine fauna with freshwater environments, but this ignores continental salt lakes and the many transitional environments (deltaic, estuarine, lagoonal, and some epicontinental seas that receive much freshwater influx, like the Baltic Sea) that separate typical marine environments from freshwater environments. This is problematic because it seems plausible that many of the late Paleozoic sediments that have been preserved were deposited on coasts in deltas and estuaries. The author had compiled a dataset of paleoenvironmental interpretations of Devonian to Early Permian stegocephalian (“tetrapod”)-bearing fossiliferous localities in 2010. How have these interpretations withstood the test of time, especially in the face of new results from different kinds of evidence? An updated dataset and a new literature review show that the case for a marine origin of stegocephalians has strengthened, especially through additional discoveries or reinterpretations of fossils that suggest marine influence in various classical vertebrate-bearing Permo-Carboniferous localities traditionally interpreted as freshwater, and a recent analysis of stable isotopes in Late Devonian localities.
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Timothy R. Smithson, Marcello Ruta & Jennifer A. Clack (2024)
On Ossirarus kierani, a stem tetrapod from the Tournaisian of Burnmouth, Berwickshire, Scotland, and the phylogeny of early tetrapods.
In: Witzmann F, Ruta M, Fröbisch N (Eds) The fish-to-tetrapod transition and the conquest of land by vertebrates .
Fossil Record 27(3): 333-352
doi:
https://doi.org/10.3897/fr.27.e126410https://fr.pensoft.net/article/126410/Recent discoveries in the Scottish Borders have greatly expanded our knowledge of post-Devonian tetrapods. Six new taxa have been named and briefly described so far. One of these, Ossirarus kierani, is represented by a single specimen from the coastal section of the Tournaisian Ballagan Formation at Burnmouth. It comprises the disarticulated bones of the posterior half of the skull, the anterior portion of the axial skeleton, and parts of the pectoral girdle and forelimbs. It is relatively small, with an estimated skull length of 54 mm. Like some Devonian tetrapods it has a preopercular and a lateral line system represented by pores. It shares with embolomeres, a tabular-parietal suture, an intertemporal and a long tabular horn. The gastrocentrous vertebrae resemble those of Caerorhachis and the brachial foramen pierces the humerus through the posterior edge, as in Mesanerpeton. Phylogenetic analyses place Ossirarus on the tetrapod stem, crownward of some – but not all – Devonian taxa. The topology of the tetrapod stem suggests that numerous lineages of Carboniferous tetrapods extended back into the Devonian.
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Ralf Werneburg & Florian Witzmann (2024)
The last eryopids: Clamorosaurus and Syndyodosuchus from the late Kungurian (Cisuralian, Permian) of Russia revisited.
In: Witzmann F, Ruta M, Fröbisch N (Eds) The fish-to-tetrapod transition and the conquest of land by vertebrates .
Fossil Record 27(3): 353-380
doi:
https://doi.org/10.3897/fr.27.e125460https://fr.pensoft.net/article/125460/The three Permian (Cisuralian) temnospondyls Syndyodosuchus tetricus, Clamorosaurus nocturnus and C. borealis from the Pechora Coal Basin in Russia, are redescribed. The assignment of Clamorosaurus to the Eryopidae is confirmed, and several new characters are presented in detail. Syndyodosuchus tetricus is identified as an eryopid for the first time, as this taxon was previously regarded as a basal stereospondylomorph. In our phylogenetic analysis, S. tetricus forms a polytomy at the base of the Eryopidae together with Actinodon frossardi and Osteophorus roemeri. More crownward, Glaukerpeton avinoffi and Onchiodon labyrinthicus build a polytomy, followed by O. thuringiensis and Stenokranio boldi as successive sister taxa of a monophyletic Clamorosaurus plus Eryops megacephalus. A reweighted analysis finds A. frossardi at the base of Stereospondylomorpha; the Eryopidae is completely resolved and consists of S. tetricus, O. roemeri, G. avinoffi, O. labyrinthicus, O. thuringiensis, S. boldi and E. megacephalus as successive outgroups to Clamorosaurus. The phylogenetic position of Clamorosaurus among the most derived eryopids is congruent with its young stratigraphic age, whereas for S. tetricus as a basal eryopid a long ghost lineage has to be assumed. Although being coeval, the two genera occurred in different environments, with Clamorosaurus being preserved in lacustrine limestones wheras S. tetricus was found in a coal bed. The lifestyle of these eryopids can best be designated as semi-aquatic.
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Raphael Moreno, Sanjukta Chakravorti, Samuel L. A. Cooper & Rainer R. Schoch (2024)
Unexpected temnospondyl diversity in the early Carnian Grabfeld Formation (Germany) and the palaeogeography of metoposaurids.
In: Witzmann F, Ruta M, Fröbisch N (Eds) The fish-to-tetrapod transition and the conquest of land by vertebrates .
Fossil Record 27(3): 381-400
doi:
https://doi.org/10.3897/fr.27.121996https://fr.pensoft.net/article/121996/
The Middle–Late Triassic Grabfeld Formation formed in a generally arid, hostile setting with frequent evaporation under alternating sabkha and playa conditions. Here we report evidence of four temnospondyl taxa from the upper part of the sequence (‘Bunte Estherienschichten’), including (1) Metoposaurus sp., (2) a capitosaur, (3) Gerrothorax sp. and (4) Plagiosternum sp. This early Carnian assemblage provides the stratigraphically oldest evidence of metoposaurids and the last report of plagiosternines in the Central European Basin. The stratigraphic age of these strata and the occurrence of Metoposauridae therein sheds new light on the palaeogeographic distribution of the group and their occurrence before the Carnian Pluvial Event.
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Rainer R. Schoch, Florian Witzmann, Raphael Moreno, Ralf Werneburg & Eudald Mujal (2024)
Growing giants: ontogeny and life history of the temnospondyl Mastodonsaurus giganteus (Stereospondyli) from the Middle Triassic of Germany.
In: Witzmann F, Ruta M, Fröbisch N (Eds) The fish-to-tetrapod transition and the conquest of land by vertebrates .
Fossil Record 27(3): 401-422
doi:
https://doi.org/10.3897/fr.27.125379https://fr.pensoft.net/article/125379/The Middle Triassic capitosaur Mastodonsaurus giganteus was the largest temnospondyl and the dominating aquatic predator in many European freshwater to brackish ecosystems. It is represented by numerous size classes, which are described and analysed for the first time. The documented size range encompasses specimens between 12–15 mm and 1200 mm in skull length. Early growth stages are restricted to dentaries and interclavicles, whereas juveniles are represented by partial skulls, mandibles, and girdles. The smallest specimens already possessed diagnostic features of the taxon, and small juveniles also shared the dermal ornament with larger specimens. The heavy, disc-shaped intercentra were established early in the juvenile phase. Cranial proportions were remarkably conservative throughout ontogeny, with the orbits proportionately decreasing in size only very moderately, the postorbital skull becoming slightly longer and the occipital margin more concave in the largest forms. Analysis of frequency distributions of M. giganteus in different Lower Keuper deposits in southern Germany reflects habitat preferences in specific phases of its life cycle. The coal-bearing deposit at Gaildorf yielded unusually large specimens with relatively well-ossified appendicular skeletons. In the more common lake shore facies, only adult specimens are present. In turn, juveniles might have dwelled in calmer environments. Smaller lakes were apparently less attractive than larger or deeper water bodies that provided sufficient resources for several temnospondyls, and juvenile specimens have been identified from all of them. The diverse actinopterygian fish fauna provided prey for all growth stages of the large temnospondyl predators.
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Pummy Roy, Sanjukta Chakravorti & Dhurjati Prasad Sengupta (2024)
Osteology and revised diagnosis of Cherninia denwai from the Middle Triassic Denwa Formation, Satpura Gondwana Basin, Central India.
In: Witzmann F, Ruta M, Fröbisch N (Eds) The fish-to-tetrapod transition and the conquest of land by vertebrates
Fossil Record 27(3): 423-443
doi:
https://doi.org/10.3897/fr.27.135664https://fr.pensoft.net/article/135664/The Middle Triassic Denwa Formation located within the Satpura Gondwana basin of Central India exhibits a significant presence of temnospondyl amphibians classified under the family Mastodonsauridae. Prior investigations have documented two taxa of the Mastodonsauridae family, namely Cherninia denwai and Paracyclotosaurus crookshanki, from the Denwa Formation. These prior accounts were predominantly predicated upon two holotype skull specimens, thereby neglecting other specimens contained within the collection as well as various associated post-cranial materials. Recently, a diverse assortment of novel specimens pertaining to C. denwai has been unearthed from the Denwa Formation. Utilizing both the newly acquired specimens and previously overlooked specimens, this study presents a redescription of C. denwai. The newly discovered specimens comprise a partial skull, a mandible, clavicles, interclavicles, vertebrae, neural arches and spines, ulnae, an ilium, a femur, and a fibula, all of which are described herein for the first time. An extensive osteological analysis of the skull and mandible is conducted. It is noted that C. denwai coexists temporally with C. megarhina, and both taxa exhibit distinct synapomorphies; however, they are recognized as separate and unique species.
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Kim Julia Kean, Marylène Danto, Celeste Pérez-Ben & Nadia Belinda Fröbisch (2024)
Evolution of the tetrapod skull: a systematic review of bone loss.
In: Witzmann F, Ruta M, Fröbisch N (Eds) The fish-to-tetrapod transition and the conquest of land by vertebrates
Fossil Record 27(3): 445-471
doi:
https://doi.org/10.3897/fr.27.133803https://fr.pensoft.net/article/133803/The simplification of the tetrapod skull occurred convergently in various tetrapod lineages from the Devonian into the Mesozoic, leading to some groups (e.g. lissamphibians) to retain only 19 of the original 41 dermal roof bones present in stem-tetrapods. Despite the potential to shed light on the functional adaptations and developmental mechanisms behind skull simplification, little work has been done on the distribution of bone loss across tetrapod phylogeny. We conducted maximum likelihood ancestral state reconstructions for the presence/absence of temporal and median dermatocranial bones using two large composite trees that placed Lissamphibia either within Temnospondyli or Lepospondyli, reflecting the ongoing debate on lissamphibian origins. Our results indicate that the temporal series did not form a developmental module, as the loss of these bones was quite variable. With the exception of Sauropsida, the intertemporal bone was lost first, followed by the supratemporal, and then the tabular and/or postparietal. In Sauropsida, the tabular and/or postparietal was the second bone to be lost. The supratemporal was lost and regained repeatedly, and was found to be the most variable element, while the nasal, frontal, and parietal were the least variable. Interestingly, the ontogenetic timing of ossification does not correlate with the propensity for a certain bone to be re-acquired or lost. No obvious relationship was found between skull simplification and lifestyle or body size. In summary, the simplification of the dermatocranium is a more complex process than previously thought, and likely involved a mixture of developmental, ecological, and functional drivers.
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Ingmar Werneburg (2024)
Terrestrialisation and the cranial architecture of tetrapods.
In: Witzmann F, Ruta M, Fröbisch N (Eds) The fish-to-tetrapod transition and the conquest of land by vertebrates
Fossil Record 27(3): 473-497
doi:
https://doi.org/10.3897/fr.27.137860https://fr.pensoft.net/article/137860/Using four extinct land vertebrate species as examples, I discuss ontogenetic strategies as well as the potential influence of bite- and other external forces on the formation of the land vertebrate skull. In principle, areas under biomechanical stress are strongly ossified, whereas regions with little or no stress show only weak or no ossification. In this regard, all plates, arcades and openings of the skull – even in that of the multi-fenestrated dinosaurs – can be explained. I trace the changes in feeding mode and body posture at the transition from semi-aquatic to fully terrestrial tetrapods and discuss changes in the position of bite points. Through evolution, an increasing bite force is argued to have a crucial influence on the formation of new skull openings, such as the supratemporal and the antorbital fenestrae in archosaurs, by changing the direction of stress flows in the skull. The conquest of land was also associated with the appearance of novel types of behaviour such as inter- and intraspecific combats. Horns and other cranial weapons were formed repeatedly, which are shown to alter skull construction when receiving external forces. Changes in the skull biomechanics are associated with body posture and postcranial skeletal anatomy. Additionally, vice versa, the neck muscles are shown to have an important impact on the differentiation of the tetrapod skull. Finally, a new hypothesis is provided for the evolution of the temporal openings, based on biomechanical considerations. I argue that the synapsid (infrafenestral) morphotype was ancestral to amniotes related to a strong anterior bite in the mouth. Along the reptilian lineage – such as in many parareptiles, captorhinids and turtles – temporal fenestration was repeatedly closed by stiffening the temporal region in response to external forces. In addition, I argue that the upper temporal opening evolved first and that the diapsid (bifenestral) morphotype is secondary. The “triapsid” morphotype in ceratopsid dinosaurs is shown to be related to concentrated forces on the animal’s neck frill.