Cristina Lombardo

NOTHOSAURID EMBRYOS FROM THE MIDDLE TRIASSIC OF NORTHERN ITALY: AN INSIGHT INTO THE VIVIPARITY OF NOTHOSAURS?

Reproductive strategies of Mesozoic aquatic reptiles are well documented only for the ichthyosaurs, which were undoubtedly viviparous since the Middle Triassic (Deeming et al., 1993; Dal Sasso and Pinna, 1996). Clear and direct evidence, such as embryos within the body of the mother, are lacking for sauropterygians. Tiny specimens of the nothosaurid Neusticosaurus (Sander, 1988) from the Middle Triassic of Monte San Giorgio (Canton Ticino, Switzerland) and of Keichousaurus (Lin and Rieppel, 1998) from China, have been interpreted tentatively as embryos, suggesting that at least some sauropterygians may have been viviparous. Recently, four additional nothosaurid embryos were found in the Monte San Giorgio area, at the Ca’ del Frate site (Viggiù, Varese, Northern Italy), and occurring in the Kalkschieferzone (Meridekalk, late Ladinian). These examples strongly support the hypothesis that nothosaurs were viviparous, particularly since three of the four embryos are clustered together in close association, excluding the possibility that they derive from isolated eggs washed into the coastal basin prior to fossilization. The fossiliferous level of the Kalkschieferzone is the youngest of five belonging to the famous paleontological area of Monte S. Giorgio-Besano-Viggiù, which has yielded vertebrates of great scientific interest since 1850 (Bürgin et al., 1989). The depositional environment of the Kalkschieferzone was a shallow complex lagoon, which formed the most protected area of a deep gulf opening toward the east (Tintori and Lombardo, 1999). Emergent land was present to the NNE, only a few kilometers away from the sites. The influence of fresh water could have been important periodically, as indicated by the presence in several levels (usually lacking vertebrates) of conchostrachans, plant remains, and insects (Tintori, 1990b; Lombardo, 1999; Krzeminski and Lombardo, 2001). To date, at least sixteen species of fishes (Lombardo, 1997, 2001) are known, along with one genus of reptiles, Lariosaurus (Tintori and Renesto, 1990; Renesto, 1993), which is represented by the holotype of L. valceresii (Tintori and Renesto, 1990), another adult specimen currently under study by one of us (SR), a juvenile (which has been referred to as Lariosaurus sp. Renesto, 1993), and the four possible embryos here described. Three of the newly discovered specimens are preserved clustered together on the same slab, while the fourth is on another slab. All four are articulated and nearly complete, lacking only those parts that were not ossified or were lost during recovery. In both cases, however, the specimens lie on a mass-mortality surface of the small fish Prohalecites, which forms more than 95% of the vertebrate remains in this fossiliferous level (Tintori, 1990a). The attribution of the four specimens to the genus Lariosaurus is based on observable characters of the skeleton. Moreover, there are no other nothosaur species in this level of the Kalkschieferzone, a situation similar to that of the pachypleurosauroids from the older fossiliferous levels of the Grenzbitumenzone and of the Meride Limestone, where only one species is present in each level (Sander, 1989). All specimens are exposed in ventral view. Three specimens (MCSNIO [Civico Museoinsubrico di Storia Naturale, Induno Olona] 701–3; Figs. 1, 2) lie close to one another and are similar in size; the fourth (MCSNIO 704; Figs. 1 and 3) lies on a different level, but is nearly identical both in shape and size to the other three. Specimens MCSNIO 701 and MCSNIO 702 are curled together, with the head of one lying in close proximity to the tail of the other. Specimen MCSNIO 703 lies with its skull close to the vertebral column of specimen MCSNIO 702 (Fig. 2), but has a straight neck and dorsal region, with only the tail curled. The overall morphology, along with all identifiable skeletal features, supports the identification of these specimens as nothosaurs. Nothosauria are a group of sauropterygian reptiles that thrived in the Middle Triassic (Rieppel and Hagdorn, 1997). In specimens MCSNIO 703 and MCSNIO 704 the cervical vertebrae number 22, and in specimen MCSNIO 702 at least four pairs of sacral ribs are detectable. This latter feature has been considered an autapomorphy of the genus Lariosaurus (Rieppel and Lin, 1995), a nothosaur of middle to large size (Rieppel, 1998) known mainly from Triassic outcrops of the Western Tethys; in addition, the number of cervical vertebrae is consistent with this attribution. Therefore, it seems reasonable to consider that the four specimens are immature individuals belonging to Lariosaurus and that their early growth stage is indicated both by absolute size and by relative proportions of different portions of the body. Even if identification of these specimens as L. valceresii seems reasonable, the lack of diagnostic characters prevents a precise species attribution; thus, they are considered as Lariosaurus sp. indeterminate.

Sexual dimorphism in a new species of the actinopterygian Peltopleurus from the Triassic of northern Italy

The new species Peltopleurus nuptialis is described on the basis of several well preserved specimens from the uppermost Ladinian Kalkschieferzone of Ca’ del Frate. This new species is characterized by small size and the presence of hook-like fulcra on all fins except the caudal, and by tubercles on the rostral and nasal bones interpreted as secondary sexual traits. There is also a modified anal fin in supposed males, which probably acted as a gonopodium, pointing to a strong sexual dimorphism. A distinctive morphological variability seems to characterize peltopleurids: a comparison with groups of living fishes also showing morphological plasticity and sexual dimorphism is given in order to hypothesize similar behaviours and adaptations in the fossil forms.

A NEW BASAL NEOPTERYGIAN FROM THE MIDDLE TRIASSIC OF LUOPING COUNTY (SOUTH CHINA)

A new taxon belonging to Neopterygians is described, based on very nicely preserved specimens from the rich vertebrate levels recently discovered in Luoping County, Yunnan Province, South China. This new assemblage dates to Pelsonian (Anisian, Middle Triassic), about the same age of the Panxian Fauna from the nearby Guizhou Province. The Luoping Fauna, yielding this new taxon, is turning out to be one of the most important fish faunas of the whole Middle Triassic and the oldest evidence of the fish radiation of this time span. This new genus of basal neopterygian shows unique derived characters, especially for the almost naked body, with a single row of urodermals covering the body lobe in the tail and a row of very small and thin scales bearing the lateral line canal along the flank. Also in the axial skeleton the new taxon shows peculiar characters such as the neural spines perfectly aligned to each paired neural arches and abdominal ribs well developed. Concerning skull bones, no suborbitals have been detected.

Feeding specializations in Late Triassic fishes

The ichthyofauna of the Zorzino Limestone represents an important proof of the richness and variety reached by bony fishes during the Norian and, at the same time, it testifies the beginning of the faunal transition which will be realized during the Jurassic. The thousands of specimens and the extraordinary quality of preservation found in the fossiliferous levels of this unit allowed, in the last years, not only to follow such a crucial moment in the evolution of vertebrates, but also to reconstruct the mode of life and the trophic adaptations reached by the different groups, living in the depositional basins. As evidence of this peculiar evolutionary period, the large predators at the highest trophic levels are still represented by ’primitive’ basal actinopterygians; on the contrary, the most derived neopterygians specialized in durophagy, a trophic niche previously almost unexploited by actinopterygians. Within the main trophic categories, anyway, we can find different morphological specializations, which probably allowed the fishes to exploit most of the available trophic resources.

OLDEST STEM TELEOSTEI FROM THE LATE LADINIAN (MIDDLE TRIASSIC) OF SOUTHERN CHINA

The origin of the largest modern vertebrate group, the Teleostei, saw major refinements in the last decades, thanks to newly discovered and stratigraphically closely spaced Triassic Lagerstatten. Here we report the oldest Pholidophoriformes (stem teleosts) that were collected during a large scale yet detailed excavation of Upper Ladinian (Middle Triassic) marine deposits in Xingyi City, Guizhou Province, China. Taxonomic comparisons support the erection of a new pholidophorid genus, Malingichthys gen. nov., with two species. The new genus shows a partially fused skull roof, a preopercular bone with a hockey-stick shape and, for the first time in Pholidophoridae, supraneural elements. Most Triassic marine vertebrate clades (fishes and reptiles, Malingichthys included) first emerged in the South China Block, with Late Ladinian most showing an important faunal transformation that was strengthened by our last findings. The material here described is about 2 million years older than the previous records for pholidophorids.

A NEW SPECIES OF THE GENUS COLOBODUS AGASSIZ, 1844 (OSTEICHTHYES, ACTINOPTERYGII) FROM THE PELSONIAN (ANISIAN, MIDDLE TRIASSIC)OF GUIZHOU, SOUTH CHINA

Eight almost complete medium-large sized (about 33 cm in s.l.) fossil fishes, belonging to the family Colobodontidae, are described from the Pelsonian (Anisian, Middle Triassic) of South China. Their cranial and postcranial features fit those of the genus Colobodus Agassiz, 1844 from the western Tethys. However, they are older than the previously known Colobodus species and, furthermore, they come far from the western Tethys, where most colobodontids have been found so far. The significance of our new findings, beyond the erection of a new species, lies in the fact that they are the first definite record of Colobodus outside the western Tethyan faunal province, and represent the oldest unequivocal colobodontids worldwide, as well as suggest that they could have originated in the East rather than the western Tethys, as previously thought.

STRUCTURE OF THE TAIL OF A PHYTOSAUR (REPTILIA, ARCHOSAURIA) FROM THE NORIAN (LATE TRIASSIC) OF LOMBARDY (NORTHERN ITALY)

The structure of the caudal portion of a vertebral column belonging to a complete phytosaur skeleton is described. The skeleton has been collected from the Calcare di Zorzino (Zorzino Limestone) of Norian (Late Triassic) age, in the small quarry of Endenna (Bergamo, Lombardy, Northern Italy). The specimen is currently being prepared, and only a detailed description of the tail is possible. The exposed portion of the skull, which shows, among other characters, a narrow, flattened snout, suggests possible relationships with the genus Mystriosuchus , but preparation of the skull must be finished prior to attempting any classification. The morphology of the tail vertebrae has never been figured for phytosaurs; however, the structure of the tail vertebrae of this specimen reflects a great degree of adaptation toward aquatic life, justifying its description prior to complete preparation. If this specimen represents a new species, it should have been highly specialised toward marine life than most other phytosaurs in which the postcranial skeleton is known.

A new species of Altisolepis (Peltopleuriformes, Actinopterygii) from the Middle Triassic of Southern China

http://zoobank.org/urn:lisid:zoobank.org:pub:9DAC36FB-CB64-4698-AEE9-CFB5D141A5D9

A new non-parasemionotiform order of the Halecomorphi (Neopterygii, Actinopterygii) from the Middle Triassic of Tethys

The halecomorph fish Panxianichthys imparilis, from the Pelsonian (Anisian, Middle Triassic) of Panxian County, Guizhou Province, South China, was recently described in brief. Here we present a thorough revision of this taxon based on 22 specimens, which allows a much better understanding of its anatomy and, consequently, its phylogenetic relationships. Newly recognized anatomical features include a flat quadratojugal, a symplectic articulating with the lower jaw ventral to the quadrate articulation, five infraorbitals, up to three suborbitals, and a large tail body lobe. Panxianichthys represents the oldest known non-parasemionotiform halecomorph and has a crescent-shaped preopercle and a maxillary branch of infraorbital sensory canal, but it is excluded from the ‘Ionoscopiformes–Amiiformes’ clade mainly by the presence of a quadratojugal, a dermosphenotic hinged to the side of the skull roof with a smooth innerorbital flange bearing no sensory canal, and a symplectic articulation much more ventral than that of the quadrate. A comparison with other Triassic non-parasemionotiform halecomorphs, together with the phylogenetic analysis, supports the erection of a new halecomorph order, Panxianichthyiformes, which is the sister group to the post-Triassic ‘Ionoscopiformes–Amiiformes’ clade. In addition, Robustichthys, also from the Anisian and previously ascribed to Ionoscopiformes, is recognized here as a new stem-group Ginglymodi. http://zoobank.org/urn:lsid:zoobank.org:pub:5594E962-985F-466D-AC52-2E9A5AC07787

The Zorzino Limestone Actinopterygian Fauna from the Late Triassic (Norian) of the Southern Alps

The ichthyofauna of the Zorzino Limestone represents an important step in the biodiversity of the bony fishes. With its richness and variety at the highest point of the Triassic, this fauna also testifies to the beginning of the faunal transition that will be realized during the Jurassic. Thousands of specimens and extraordinary preservation of the fossils yielded by these levels have allowed the monitoring of such a crucial moment in the evolution of vertebrates. These favourable conditions allowed also the reconstruction of the mode of life and the trophic adaptations performed by the different fish groups that dwelled in those depositional basins surrounded by the largest carbonate platform ever, now known as the Dolomia Principale (or Haupt Dolomite of German-speaking geologists). As further proof of this peculiar evolutionary period, the large predators occupying the highest trophic levels were still represented by ‘primitive’ basal actinopterygians; on the contrary, the most derived neopterygians developed a specialization in durophagy, a trophic niche formerly unexploited by actinopterygians. Within the main trophic categories, we can find different morphological specializations, which probably allowed the fishes to exploit most of the available trophic resources. The blooming of the stemgroup Teleostei, the Pholidophoriformes, is also recorded, with several genera occurring together in the best represented localities.