New insights for ancient foraminifera through 3D visuals of fusulinids Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Yu-Kun Shi, Hao Huang, Zong-Hang Shen Abstract Fusulinids are larger benthic foraminifera of late Paleozoic and index fossils for Permo-Carboniferous strata. The traditional methods to examine their internal structures are through ground thin sections, which however caused lots of ambiguities regarding the morphological diagnostics and taxonomic identification. In recent years, new technique of high resolution X-ray computed tomography sheds light on the microfossil examination and we had fusulinid individuals successfully processed with this innovative approach. Here we present the results of 19 Pseudofusulina specimens, including high resolution images and rendered three-dimensional (3D) visuals of the important internal structures, to unwrap more details of fusulinid morphology. This is the first time the full 3D visuals of fusulinid interiors were constructed and exhibited. Previous understandings on fusulinid basic morphology, such as proloculus, chamber development, are precisely described with 3D illustration; cuniculi and phrenotheca are discovered regularly among the specimens and therefore are not suggested to be diagnostic features of taxonomic splitting; test and proloculus morphology divergences caused by section orientation are captured. With assistance of high resolution CT technique, fusulinid morphology, especially internal structures, is much easier to acquire, understand, and exhibit, despite the critical limitation that only the fusulinid samples buried with terrigenous clasts, such as those from calcareous mudstone or argillaceous limestone, could be successfully scanned.

Striking case of convergence — Alleged marine gastropods in Cretaceous Burmese amber are terrestrial cyclophoroids. Comment on Yu et al. Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Thomas A. Neubauer, Barna Páll-Gergely, Adrienne Jochum, Mathias Harzhauser Abstract Yu et al. (2019) recently described two new species of gastropods from the Cretaceous Burmese amber and attributed them to the marine family Epitoniidae. A close inspection of the images provided by Yu et al. indicates however that the species in question do not belong to that family or any marine gastropod group. In contrast, the two species are attributed here to the terrestrial operculate family Pupinidae (Cyclophoroidea) and tentatively to the genus Pseudopomatias. We briefly review the fossil record of the Cyclophoroidea and Pupinidae and discuss implications of the present revision. After all, Pseudopomatias? lyui (Yu, Wang and Jarzembowski, 2019) and P.? zhuoi (Yu, Wang and Jarzembowski, 2019) belong to the oldest members of the Pupinidae.

The postparietal shield of the Pragian dipnomorph Arquatichthys and its implications for the rhipidistian cranial anatomy Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Jing Lu, Min Zhu Abstract Rhipidistians comprise dipnomorphs (the lungfish lineage) and tetrapodomorphs (the tetrapod lineage). Arquatichthys porosus Lu and Zhu, 2008 is a Pragian dipnomorph from the Posongchong Formation of Zhaotong, Yunnan, South China (∼409 million years ago, Early Devonian), previously represented by a lower jaw and few scattered scales. Here we describe a newly-discovered postparietal shield of Arquatichthys by means of high-resolution computed tomography. The cranial morphology of Arquatichthys resembles that of the basal dipnomorph Powichthys in having more than two supratemporal bones each side, more than one row of openings for sensory canals on the marginal bones, and a straight posterior margin of the shield. An intricate occipital artery system is present between the skull roof and neurocranium, as in Youngolepis and the tetrapodomorph Eusthenopteron. The discovery of the postparietal shield of Arquatichthys adds new evidence in the cranial evolution of rhipidistians, and helps to improve our understanding of the character transformations during the early diversification of rhipidistians.

The Upper Devonian tetrapodomorph Gogonasus andrewsae from Western Australia: Reconstruction of the shoulder girdle and opercular series using X-ray Micro-Computed Tomography Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Yu-Zhi Hu, Gavin C. Young, Jing Lu Abstract The tetrapodomorph fish, Gogonasus andrewsae is a three dimensionally well-preserved sarcopterygian from the Gogo Formation (Frasnian, early Upper Devonian, ∼380 million years ago) in Western Australia. High-resolution X-ray Micro-Computed Tomography and 3D printouts were used to obtain a digital reconstruction of its shoulder girdle and opercular series. Our new findings show the opercular series in a close fit against the upper bones of the shoulder girdle only if the anocleithrum, supracleithrum and post-temporal are aligned more horizontally than in previous reconstructions. The lowermost subopercular bone also differs, in partly covering the clavicle of the shoulder girdle. The ascending process of the clavicle, and the ventral process of the anocleithrum, do not fit closely inside the cleithrum, and perhaps functioned for ligamentous attachment. A rugose area on the anocleithral process is in a similar relative position to the attachment of a muscle ligament on the shoulder girdle of various living actinopterygians. Our manipulation of 3D printouts permits testing of the morphological fit of extremely fragile acid-etched bones, and indicates a new way to investigate the constructional morphology of one or more mechanical units of the vertebrate skeleton. It is suggested that Micro-CT imaging, reconstruction, visualisation and 3D printing techniques will provide a rigorous new test leading to modification of previous reconstructions of extinct vertebrates that were based on graphical methods and 2D imaging.

High resolution XCT scanning reveals complex morphology of gnathal elements in an Early Devonian arthrodire Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Yu-Zhi Hu, G.C. Young, Carole Burrow, You-an Zhu, Jing Lu Abstract Arthodire placoderms, as a possible sister group of Chinese ‘maxillate’ placoderms plus crown gnathostomes, provide important information regarding early evolution of jaws and teeth. High-resolution computed tomography and digital dissection on a unique articulated 400 million-year-old buchanosteid arthrodire permitsa detailed description of the three types of gnathal elements in basal arthrodires for the first time, giving insights into their morphology and the organization of the associated dentition. In displaying numerous denticle rows (dental fields), the gnathal element morphology is very different from the much-reduced denticulation of higher brachythoracid arthrodires, even though the latter have been used recently to interpret origin and early evolution of teeth. Ossification centres are anterolateral on the anterior supragnathal (attached to the braincase), anteromesial on the posterior supragnathal (attached to the palatoquadrate), and in the central part of the biting portion of the infragnathal (attached to the meckelian cartilage). The latter bone shows no evidence of two ossification centres as has been interpreted for more advanced arthrodires. Denticle rows radiating from the ossification centre form dental fields in all three elements, and are more similar to the gnathal elements of phlyctaeniid and actinolepid arthrodires than to advanced brachythoracids. The new evidence gives insights into the primitive arthrodire condition for comparison with the dermal jaw bones of Chinese ‘maxillate’ placoderms that have been homologised with the premaxilla, maxilla, and dentary of osteichthyans. The new details will help clarify the sequence of character acquisition in the evolution of marginal jaw bones in basal gnathostome groups.

Tomographic reconstructions of crab burrows from deltaic tidal flat: Contribution to palaeoecology of decapod trace fossils in coastal settings Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Yuan-Yuan Wang, Xue-Qin Wang, Bin Hu, Mao Luo Abstract Trace fossils play an important role in reconstructing palaeoecology and depositional environment. Their palaeoecological implications can be better understood when the trace makers are correctly identified. Neoichnology studies the burrow morphologies, behavioral ecology of modern organisms and their interaction with the environment. Neoichnology is of great significance in linking burrowing behaviors of extant organisms with interpretation of trace fossil palaeoecology. This paper reports a study on burrows produced by the ocypodid crab (Macrophthalmus japonicus De Haan) in the tidal region of the Yellow River Delta using CT scanning techniques. Our results show that M. japonicus produces abundant I-, U-, and Y-shaped burrows in a mudflat of the delta. These domicile structures are similar in morphological characteristics to the trace fossil Psilonichnus, suggesting M. japonicus as its possible additional trace maker. Our study supports the usage of Psilonichnus as a significant palaeoenvironmental indicator for coastal and shelf environments. Furthermore, this study highlights the great potential of applying CT techniques in future ichnological-related studies.

First record of marine gastropods (wentletraps) from mid-Cretaceous Burmese amber Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Ting-Ting Yu, Bo Wang, Ed Jarzembowski Abstracts Gastropod fossils are rarely preserved in amber with only a few records of terrestrial snails. Two new species, Epitonium (Epitonium) zhuoi n. sp. and Epitonium (Papyriscala) lyui n. sp. are described based on two well-preserved specimens from mid-Cretaceous amber from northern Myanmar. Highresolution three-dimensional images using X-ray micro-computed tomography (micro-CT) are provided. These species can be attributed to the family Epitoniidae (wentletraps) based on the shell characters such as the slender and conical shell-shape, numerous whorls, round aperture and regular, axial sculpture of high, sharply-ribbed costae. Our find is the first record of marine gastropods preserved in amber, and suggests that the Burmese amber forest probably existed close to the seashore.

A marattialean fern, Scolecopteris libera n. sp., from the Asselian (Permian) of Inner Mongolia, China Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Dan-Dan Li, Jun Wang, Shan Wan, Josef Pšenička, Wei-Ming Zhou, Jiří Bek, Jana Votočková-Frojdová Abstract Scolecopteris libera n. sp. is established on partial three-dimensionally preserved materials containing both sterile and fertile fronds collected from the volcanic tuff at the top of the Taiyuan Formation at the Wuda Coalfield, Inner Mongolia, China. It is characterized by tripinnate fronds with rachises over 200 mm in diameter; and long lanceolate or falciform pinnules with thick veins. Pinnules are of the pecopterid-type, with those at the base of the ultimate pinnae usually divided into small lobes. Eight to twelve circular synangia are arranged in two rows along the midvein. Synangia are borne on a short pedicel attached to the middle of lateral veins. A synangium is composed of 7–10 fusiform exannulate sporangia with pointed apices. The sporangia are free among each other beyond the base of synangia. In situ microspores of the Cyclogranisporites leopoldii type differ from all other in situ Paleozoic marattialean spores.

The bony labyrinth of Platecarpus (Squamata: Mosasauria) and aquatic adaptations in squamate reptiles Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Hongyu Yi, Mark Norell Abstract Mosasaurs were among the last marine reptiles that lived before the Cretacesous–Paleogene extinction. Little is known about the sensory evolution of mosasaurs in relation to their aquatic lifestyle. In this study, the braincase of Platecarpus was CT-scanned and virtual models were constructed showing the bony labyrinth — or the inner ear — a sensory apparatus for balance and hearing. The virtual inner ear consists of the semicircular canals, vestibule, and cochlea. Compared with extant squamates, Platecarpus resembles sea snakes in having a small vestibule with a flat dorsal surface, but it differs from non-mosasaurian squamates in having rounded semicircular canals. Phylogenetic linear regression analysis supports a linear relationship, independent from phylogeny, between the length of the three semicircular canals and the length of the skull. The semicircular canals of Platecarpus are shorter than predicted, but the fossil data fell within the 95% prediction interval calculated from the extant data and the skull length of Platecarpus. Although size reduction of the bony labyrinth has been associated with aquatic adaptions in mammals, our results suggest that in squamates, semicircular canal size is related to skull size rather than habitat preference.

Tubular microfossils from the Ediacaran Weng’an Biota (Doushantuo Formation, South China) are not early animals Publication date: December 2019 Source: Palaeoworld, Volume 28, Issue 4 Author(s): Wei-Chen Sun, Zong-Jun Yin, Philip Donoghue, Peng-Ju Liu, Xiao-Dong Shang, Mao-Yan Zhu Abstract The early Ediacaran Weng’an Biota (ca. 609 Ma) of the Doushantuo Formation (Guizhou Province, China) encompasses an abundant and exquisitely preserved assemblage of phosphatic microfossils that have provided unique insight into the origin and early evolution of multicellular eukaryotes. However, the affinities of these early organisms are far from certain, including the tubular microfossils Crassitubulus, Quadratitubus, Ramitubulus, and Sinocyclocylcicus. These taxa have been widely accepted as stem-cnidarians or, alternatively, interpreted as filamentous cyanobacteria, or multicellular algae. We use high-resolution X-ray tomographic microscopy to analyse the structure and development of the four taxa. Our data and analysis allow us to conclude that these four taxa were not biomineralized. Crassitubulus, Quadratitubus, and Sinocyclocylcicus, may be grouped on the basis that they exhibit alternating complete and incomplete cross walls, and bipolar growth; which makes them favourably comparable to filamentous cyanobacteria. In contrast, Ramitubulus exhibits only complete cross walls, unipolar growth and dichotomous branching. These features are difficult to reconcile with a cyanobacterial interpretation. They are, instead, more indicative of multicellular algae-like Cambrian Epiphyton. Thus, the Weng’an tubular microfossils constitute a disparate assemblage of cyanobacteria and algae, but none represents early Ediacaran animals.