Bollettino SPI Vol. 58 (3)
Published in December 2019
- Lucas S.G. (2019) – INVITED PAPER – OPEN ACCESS!
An ichnological perspective on some major events of Paleozoic tetrapod evolution
Tetrapod trace fossils (primarily footprints) provide signifi cant insight into some major events of the Paleozoic evolution of tetrapods. The oldest fossils of tetrapods are Middle Devonian footprints from Ireland. Bona fi de Devonian tetrapod footprints indicate lateral sequence walking by quadrupedal tetrapods with a smaller manus than pes. These trackways indicate that tetrapods other than “ichthyostegalians” remain to be discovered in the Devonian body-fossil record. Devonian tetrapod footprints are from nonmarine paleoenvironments, so they do not support a marginal marine/marine origin of tetrapods. Nevertheless, the Devonian tetrapod footprint record is too sparse to be of paleobiogeographic signifi cance and to evaluate unsubstantiated claims of Late Devonian tetrapod mass extinctions. “Romer’s gap”, a supposed paucity of Early Mississippian terrestrial fossils, has largely been fi lled by sampling and description of already known fossils. It includes the fi rst substantial assemblage of tetrapod footprints, from Blue Beach, Nova Scotia, Canada. This assemblage consists of footprints of small and large temnospondyls and reptiliomorphs, which supports the concept that the Carboniferous diversifi cation of terrestrial tetrapods had begun during (or before) Tournaisian time. No defi nite pre-Pennsylvanian amniote footprints are known, so the Early Pennsylvanian age of the oldest amniote footprints and body fossils is the same. The Kasimovian revolution was a prolonged and complex change across the Middle-Late Pennsylvanian boundary from the “coal forests” to a more xerophytic vegetation accompanied by changes and “sluggish evolution” in the marine biota and the appearance of new tetrapod taxa in the body-fossil record, notably the oldest high fi ber herbivores, the diadectomorphs and the edaphosaurid eupelycosaurs. However, the tetrapod footprint record changes little during the Kasimovian and documents much older records of diadectomorph and eupelycosaur (possible edaphosaurs) footprints in the Bashkirian, thus diminishing the extent of tetrapod originations during the Kasimovian revolution.
The Permian tetrapod footprint record is much more extensive and better understood than the Carboniferous footprint record. Tetrapod footprints confi rm the body-fossil record in demonstrating no signifi cant changes in tetrapod evolution took place across the Carboniferous-Permian boundary. The late early Permian sauropsid radiation is best documented by a change in the tetrapod footprints from synapsid- and non-amniote-dominated assemblages to those dominated by the footprints of captorhinomorphs and parareptiles. Early Permian tetrapod footprints from eolian sediments demonstrate the colonisation of deserts by tetrapods. Olson’s gap is a global hiatus in the tetrapod body-fossil record during which eupelycosaur-dominated assemblages of the early Permian were replaced by therapsid-dominated assemblages of the middle-late Permian. The gap in the body fossil record corresponds to most of Kungurian time, and the tetrapod footprint record indicates an abundance of captorhinomorph footprints and very few eupelycosaur footprints just before and during Olson’s gap, suggesting that the extinction of the eupelycosaurs had already begun well before the fi rst appearance of therapsids. The substantial extinction of dinocephalian therapsids and other tetrapods at approximately the end of the middle Permian, the dinocephalian extinction event, is well documented by the tetrapod footprint record in paleoequatorial Pangea, where there is a paucity of tetrapod body fossils during this interval. The lack of an end-Permian tetrapod mass extinction fi nds support in the tetrapod footprint record because most late Permian tetrapod footprint ichnogenera continue into the Triassic. Late Permian archosauriform footprints add evidence that their diversifi cation, and the upright gait, began during the Permian. Most Paleozoic tetrapod trackways indicate quadrupedal lateral sequence walking with a sprawling gait, but relatively narrow gauge tetrapod trackways as old as Carboniferous may indicate some semi-upright to upright walking. Defi nite upright walking is demonstrated by late Permian therapsid and archosauriform footprints, and no know footprints of bipedal tetrapods are known from Paleozoic strata, although a few Permian tetrapod taxa known from skeletons may have been bipeds. Besides footprints, other Paleozoic tetrapod trace fossils (bromalites, burrows and dentalites) are too poorly known and too little studied to provide much insight into Paleozoic tetrapod evolution. Nevertheless, the tetrapod footprint record documents key events in Devonian-Permian tetrapod evolution and needs to be part of a complete understanding of Paleozoic tetrapod evolutionary history.
- Reyes-Abril J., Villas E. & Gutierrez-Marco J.C. (2019)
Middle Ordovician strophomenoid brachiopods from the high latitude Gondwanan shelves (Central Spain) and their travel route
Two strophomenoid brachiopods from the Middle Ordovician of the Toledo Mountains, Central Spain, representing the first arrival of the group to the high latitude Gondwanan shelves are described. They are the new genus and species Oretanomena meloui, from the Navas de Estena Shales and Río Shales, Oretanian (mid Darriwilian) in age, and Dactylogonia asturica, from the Guindo Shales, Dobrotivian (late Darriwilian) in age. Oretanomena is a primitive strophomenid of concavo-convex, dorsally geniculate profile, very close to the Iranian Semnanostrophia. They both settled during mid Darriwilian times on the high latitude Gondwanan shelves, much probably originating from South China ancestors after a migration along the western Gondwanan coast. Dactylogonia asturica settled on the Iberian platform slightly later, during the late Darriwilian, as the result of the dispersion of its genus from Laurentia, crossing the Iapetus Ocean up to Avalonia, and then also the Rheic Ocean, up to the Mediterranean margin of Gondwana. Dactylogonia is added to other rare rhynchonelliform brachiopods that succeeded in crossing the Rheic Ocean, during a time of strong faunal isolation of the high latitude margin of Gondwana.
- Georgalis G.L., Arca M., Rook L., Tuveri C. & Delfino M. (2019)
A new colubroid snake (Serpentes) from the early Pleistocene of Sardinia, Italy
We herein describe Sardophis elaphoides Georgalis & Delfino n. gen. n. sp., a new snake taxon from the early Pleistocene of Monte Tuttavista VI, Sardinia, Italy. Sardophis elaphoides Georgalis & Delfino n. gen. n. sp. possesses a distinct vertebral anatomy and is diagnosed by a unique combination of features. The new Sardinian taxon is further compared in detail and differentiated from all extant European and North African snake species. Although the affinities of Sardophis elaphoides Georgalis & Delfino n. gen. n. sp. with colubroids are clear, its more inclusive relationships within that clade cannot be resolved with certainty. Being an insular form, Sardophis elaphoides Georgalis & Delfino n. gen. n. sp. adds significantly to our so far poor knowledge of island endemic snakes. An overview of the fossil record of snakes from the Mediterranean islands is provided. The new species increases the number of reptile taxa that went extinct in Sardinia during the late Neogene and Quaternary.
- Carnevale G. & Bannikov A.F. (2019)
A dragonet (Teleostei, Callionymoidei) from the Eocene of Monte Bolca, Italy
A new callionymoid fish, †Gilmourella minuta n. gen. n. sp., is described herein based on a single specimen from the Eocene locality of Monte Bolca, northern Italy. †Gilmourella minuta n. gen. n. sp. differs from other callionymoids (families Callionymidae and Draconettidae) by having a large and elongate head, snout well-development, thin opercular bones, a preopercle with a posterior blunt spine, a ribbon-like interopercle, a subtriangular opercle with fimbriated posterior margin, an elongate and distally pointed subopercle, 18 (7+11) anteroposteriorly compact vertebrae, a caudal fin with 14 short rays, absence of the spinous dorsal-fin, dorsal and anal fins with five unbranched rays, and short pelvic fins. Within the callionymoids, †Gilmourella n. gen. shares a number of features (strongly protractile upper jaws, absence of the endopterygoid, the hypurals and parhypural consolidated into single plate, the haemal spine of penultimate vertebra fused to centrum, anal-fin rays being mostly unbranched) with the Callionymidae and together they seem to form a sister pair. In addition a brief discussion of the fossil record of the dragonets reveals that †Gilmourella minuta n. gen. n. sp. represents the oldest record for the callionymoid fishes known to date.
- RASSEGNA DELL’ATTIVITÀ SOCIALE
Adunanza dell’Assemblea dei Soci della Società Paleontologica Italiana
– Soprintendenza Archeologia, Belle Arti e Paesaggio per le province di Caserta
e Benevento, Viale degli Atlantici 14/16, Benevento (BN) –
24 Maggio 2019
La conservazione dei beni paleontologici: stato dell’arte e aspetti da valorizzare 6 Maggio 2019 – Firenze