Carlo Romano | University of Zurich, Switzerland (original) (raw)

Papers by Carlo Romano

Freiberger Forschungshefte, 2016

The Saurichthyidae (Actinoperygii, Osteichthyes) are a long-lasting family, ranging from the late... more The Saurichthyidae (Actinoperygii, Osteichthyes) are a long-lasting family, ranging from the latest Permian to the
Middle Jurassic (~75 million years) and including nearly 50 species, most of which belong to the essentially
Triassic genus Saurichthys. At least 14 species occur in the Early Triassic, but many of them are only scarcely
known, leading to a gap of knowledge of their early evolution. Four species have been described from the Early
Triassic of Spitsbergen (Svalbard archipelago, Arctic Norway): Saurichthys wimani, S. ornatus, S. elongatus and
S. hamiltoni. These taxa are based predominantly on cranial material, whereas postcrania, which contain more
diagnostic features in Saurichthys, are extremely rare. We present the eighth saurichthyid postcranium from
Spitsbergen, which was collected during the 2008 Swiss-Norwegian expedition to Stensiöfjellet (Mount Stensiö),
Sassendalen. The new specimen is the most complete saurichthyid postcranial segment known from Spitsbergen,
preserving the portion between the pelvic girdle and the caudal fin, and is ascribed to S. wimani based on the
squamation. S. wimani can now be characterized by the following set of postcranial traits: (1) all fins with
segmented and branched lepidotrichia and fringing fulcra along their leading edge, (2) rows of large, ornamented
scales in mid-dorsal, mid-ventral and mid-lateral position and small, rhombic dorsolateral scales (the ventrolateral
scale row being probably absent), and (3) a vertebral column consisting of (dorsal) neural arches with small praeand
postzygapophyses and distinct neural spines, relating as 2:1 to the mid-lateral scales, and to the (ventral)
haemal arches as 2:1 in the abdominal and as 2:2 in the caudal body portion. Mid-lateral scales of the caudal
peduncle bear denticles on their ventrocaudal margin, previously unknown in saurichthyids. At least three species
of Saurichthys are distinguishable in the Smithian aged ‘fish horizon’ of Spitsbergen based on postcranial
characters, supporting a fast diversification of saurichthyids following the great end-Permian mass extinction
event.

Journal of Zoology, 2021

The postcranial axial skeleton of actinopterygian fishes is typically divided into three regions:... more The postcranial axial skeleton of actinopterygian fishes is typically divided into three regions: (1) an anterior abdominal region, (2) a posterior caudal region and (3) those vertebrae supporting the caudal fin. However, in some actinopterygians, the axial skeleton is more finely subdivided, with up to six morphologically distinct sub-regions recognized. Phylogenetic continuity and homology of structures across these sub-regions have not been investigated in detail, either between or among groups. We examine variation in axial regionalization in saurichthyid fishes, a clade of extinct non-teleostean actinopterygians with highly variable axial skeletal morphology but an otherwise conservative body plan, and compare these findings to other non-teleostean actinopterygians to assess conservation of a regionalized axial skeleton within bony fishes. We document up to eight distinct regions in the vertebral column of Triassic Saurichthys: (1) a postoccipital region, (2) an anterior and (3) a posterior abdominal region, (4) a transitional region spanning the abdominalcaudal boundary, (5) an anterior and (6) a posterior caudal region and (7) preural and (8) ural regions. Based on taphonomical and morphological evidence, the transitional region appears to function in axial stiffening in the area of the median fins, whereas the abdominal region is highly flexible. The degree to which these axial regions are osteologically differentiated is highly variable across Saurichthyidae, implying iterative evolution of differentiation and de-differentiation over relatively short geological timescales. Such variably expressed regionalization was also identified in the outgroup non-teleostean actinopterygians Birgeria and Australosomus. Despite variation in morphological disparity, the regions identified in saurichthyids correlate well with those documented in some teleosts and Paleozoic actinopterygians, suggesting potential deep patterning homology but independent evolution of specific regionalized axial morphologies in response to changing functional demands.

Frontiers in Earth Science, 2021

About half of all vertebrate species today are ray-finned fishes (Actinopterygii), and nearly all... more About half of all vertebrate species today are ray-finned fishes (Actinopterygii), and nearly all of them belong to the Neopterygii (modern ray-fins). The oldest unequivocal neopterygian fossils are known from the Early Triassic. They appear during a time when global fish faunas consisted of mostly cosmopolitan taxa, and contemporary bony fishes belonged mainly to non-neopterygian (“paleopterygian”) lineages. In the Middle Triassic (Pelsonian substage and later), less than 10 myrs (million years) after the Permian-Triassic boundary mass extinction event (PTBME), neopterygians were already species-rich and trophically diverse, and bony fish faunas were more regionally differentiated compared to the Early Triassic. Still little is known about the early evolution of neopterygians leading up to this first diversity peak. A major factor limiting our understanding of this “Triassic revolution” is an interval marked by a very poor fossil record, overlapping with the Spathian (late Olenekia...

Journal of Paleontology

A new locality for low-latitudinal, Early Triassic fishes was discovered in the Candelaria Hills,... more A new locality for low-latitudinal, Early Triassic fishes was discovered in the Candelaria Hills, southwestern Nevada (USA). The fossils are derived from the lower Candelaria Formation, which was deposited during the middle–late Dienerian (late Induan), ca. 500 ka after the Permian-Triassic boundary mass extinction event. The articulated and disarticulated Osteichthyes (bony fishes), encompassing both Actinistia (coelacanths) and Actinopterygii (ray-fins), are preserved in large, silicified concretions that also contain rare coprolites. We describe the first actinopterygians from the Candelaria Hills. The specimens are referred to Pteronisculus nevadanus new species (Turseoidae?), Ardoreosomus occidentalis new genus new species (Ptycholepidae), the stem neopterygian Candelarialepis argentus new genus new species (Parasemionotidae), and Actinopterygii indet. representing additional taxa. Ardoreosomus n. gen. resembles other ptycholepids, but differs in its more angulate hyomandibula ...

Journal of Paleontology

The Early Triassic vertebrate record from low paleolatitudes is spotty, which led to the notion o... more The Early Triassic vertebrate record from low paleolatitudes is spotty, which led to the notion of an ‘equatorial vertebrate eclipse’ during the Smithian. Here we present articulated ray-finned fishes (Actinopterygii), collected from the marine Lower Triassic Thaynes Group at three new localities in Elko County (Nevada, USA), which were deposited within the equatorial zone. From the Smithian of the Winecup Ranch, we describe two partial skulls of the predatory actinopterygian Birgeria (Birgeriidae), attributed to B. americana new species and Birgeria sp. Birgeria americana n. sp. is distinguished from other species by a less reduced operculogular series. With an estimated total length of 1.72–1.85m, it is among the largest birgeriids. We confirm that Birgeria encompasses species with either two or three rows of teeth on the maxilla and dentary, and suggest that species with three well-developed rows are restricted to the Early Triassic. From the latest Smithian of Palomino Ridge, we...

ABSTRACT Recovery from the end-Permian mass extinction is frequently described as delayed, with c... more ABSTRACT Recovery from the end-Permian mass extinction is frequently described as delayed, with complex ecological communities typically not found in the fossil record until the Middle Triassic epoch. However, the taxonomic diversity of a number of marine groups, ranging from ammonoids to benthic foraminifera, peaked rapidly in the Early Triassic. These variations in biodiversity occur amidst pronounced excursions in the carbon isotope record, which are compatible with episodes of massive CO2 outgassing from the Siberian Large Igneous Province. Here we present a high-resolution Early Triassic temperature record based on the oxygen isotope composition of pristine apatite from fossil conodonts. Our reconstruction shows that the beginning of the Smithian substage of the Early Triassicwas marked by a cooler climate, followed by an interval of warmth lasting until the Spathian substage boundary. Cooler conditions resumed in the Spathian. We find the greatest increases in taxonomic diversity during the cooler phases of the early Smithian and early Spathian. In contrast, a period of extreme warmth in the middle and late Smithian was associated with floral ecological change and high faunal taxonomic turnover in the ocean. We suggest that climate upheaval and carboncycle perturbations due to volcanic outgassing were important drivers of Early Triassic biotic recovery.

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Epic3bremerhaven Pangaea, 2012

ABSTRACT We survey the fossil record of predation in saurichthyids based on some new and restudie... more ABSTRACT We survey the fossil record of predation in saurichthyids based on some new and restudied material from the Triassic and document several fossils with ingested fishes and even one specimen with possible remains of a small tetrapod. Although, unlike teleostean fishes, the paleopterygian saurichthyids did not evolve a mechanism to enlarge the mouth cavity, they apparently were able to catch and engulf relatively big animals. Yet, swallowing large prey frequently had lethal consequences, as can be seen in several specimens of Saurichthys with congeneric individuals of nearly equal body length as the predator itself stuck in the predator”s mouth. Predatory fishes that succumbed from engulfing overly large prey are known from both fossil and recent examples.

Supplement to Romano Carlo Goudemand Nicolas Vennemann Torsten W Ware David Schneebeli Hermann Elke Hochuli Peter a Bruhwiler Thomas Brinkmann Winand Bucher Hugo Climate and Biotic Upheavals Following the End Permian Mass Extinction Nature Geoscience 6 57 60 Doi 10 1038 Ngeo1667, Dec 21, 2013

Freiberger Forschungshefte, 2016

Journal of Zoology, 2021

Frontiers in Earth Science, 2021

Journal of Paleontology

Http Dx Doi Org 10 1080 02724634 2010 521962, Nov 1, 2010

Epic3bremerhaven Pangaea, 2012

Mass extinction events near the Palaeozoic/Mesozoic boundary had a major impact on life on Earth.... more Mass extinction events near the Palaeozoic/Mesozoic boundary had a major impact on life on Earth. Here we present an updated analysis of the diversity dynamics and size changes of Chondrichthyes and Osteichthyes during the Permian/Triassic. We show that chondrichthyan genus diversity declined during the Middle–Late Permian. Many Palaeozoic groups (e.g. Petalodontiformes) were largely replaced by hybodonts and modern sharks (Neoselachii). A significant overall decrease in tooth size and body length observed across the Permian/Triassic boundary suggests a selective loss of large-sized chondrichthyans. The largest extinction occurred amongst marine groups, with benthic and pelagic groups suffering most, but selectivity for these palaeoecological traits is not evident. Osteichthyes show a general pattern of low diversity during the Permian to higher levels in the Triassic, leading to increased diversity among the modern ray-finned fishes (Neopterygii). Palaeopterygii experienced a significant increase in body size across the Middle/Late Permian boundary and remain among the larger fishes during the Triassic. Neopterygians mostly remained smaller and, thus, mostly occupied lower positions within aquatic food webs. Our data indicates an important evolutionary turnover among fishes, changing from chondrichthyan-dominated communities of the Carboniferous–Permian to osteichthyan (actinopterygian)-dominated associations of the Meso- and Cenozoic.

Mass extinction events near the Palaeozoic/Mesozoic boundary are evidence of a major upheaval in ... more Mass extinction events near the Palaeozoic/Mesozoic boundary are evidence of a major upheaval in the biosphere. While patterns and processes of extinction and recovery of Permian–Triassic marine invertebrates and terrestrial vertebrates are relatively well studied, little is known about fishes during this critical interval. Here we present an updated analysis of the diversity dynamics and size changes of Permian–Triassic cartilaginous fishes (Chondrichthyes) and bony fishes (Osteichthyes). We show that chondrichthyan genus diversity declined during the Middle–Late Permian, supporting a combined overall extinction as a result of the end-Guadalupian and Late Permian events. Many Palaeozoic groups (e.g., Cladodontomorphi, Petalodontiformes) were largely replaced by hybodonts and modern sharks (Neoselachii). Holocephalans and xenacanths survived into the Triassic but at low diversity levels. Eugenodontiformes went extinct in the Early Triassic. A significant overall decrease in tooth size and body length observed across the Permian/Triassic boundary suggests a selective loss of large-sized chondrichthyans. The largest extinction occurred amongst marine groups, with benthic and pelagic groups suffering most, but selectivity for these palaeoecological traits is not evident. In contrast to Chondrichthyes, Osteichthyes experienced diversification events during the Early Triassic and Middle Triassic, resulting in a general pattern of low diversity during the Permian to higher levels in the Triassic. This Triassic radiation of bony fishes led to increased diversity among the modern ray-finned fishes (Neopterygii), which comprise the bulk of today’s fish faunas. Furthermore, Palaeopterygii experienced a significant increase in body size across the Middle/Late Permian boundary and these fishes remain among the larger fishes during the Triassic. Neopterygians mostly remained smaller and, thus, mostly occupied lower positions within aquatic food webs. Our data supports previous findings of an important evolutionary turnover among fishes, changing from chondrichthyan-dominated communities of the Carboniferous–Permian to osteichthyan(actinopterygian)-dominated associations of the Meso- and Cenozoic.

The Permian and Triassic were important time intervals for the evolution of life on Earth due to ... more The Permian and Triassic were important time intervals for the evolution of life on Earth due to the effects of the late Permian mass extinction, the most devastating biotic crisis of the Phanerozoic. This event restricted the diversity of or even wiped out many Palaeozoic groups and ultimately enabled the radiation of typically Mesozoic but also more modern clades. Although the impact of the late Permian event and the subsequent biotic recovery has been intensively studied for some groups, predominantly invertebrates and terrestrial tetrapods, its implications for fishes (Osteichthyes, Chondrichthyes) are still not well understood. Almost nothing is known about the consequences of other biotic crises of the Permian–Triassic interval for fishes, such as the end-Guadalupian event (Middle Permian) or the Smithian/Spathian boundary event (Early Triassic). We present a state-of-the-art analysis of the Permian and Triassic record of Osteichthyes (Dipnoi, Actinistia, Actinopterygii) focussing on patterns in diversity and body size change in order to elucidate the response of bony fishes to the late Permian extinction and other important biotic crises of the studied interval. Our results show that osteichthyans were subject to large fluctuations in diversity and that different patterns emerge from the marine and the non-marine record. In summary, diversity of marine bony fishes is considerably higher in the Triassic than in the Permian, with a major peak in the Middle Triassic. In the freshwater record, a diversity decline is noted in the Early Permian, coinciding with “Olson’s gap” postulated for terrestrial vertebrates. Triassic diversity of freshwater osteichthyans does not exceed that of the Permian. While no decline in overall diversity at the Permian/Triassic boundary is observed in the marine realm, a diversity minimum occurs during the Early Triassic for freshwater osteichthyans. However, the latitudinal diversity gradient of marine bony fishes during the Early Triassic was different than at other times. In the marine realm, we note a distinct increase in body size in the late Permian in palaeopterygians, the then dominant group of bony fishes, followed by two important origination events, one in the Early Triassic, related with the diversification of ‘subholosteans’, and one in the Middle Triassic, based on increased originations of both ‘subholostean’ and neopterygian taxa. Judging from the predominantly smaller body sizes of ‘subholosteans’ and neopterygians, these novel forms are to be expected on lower trophic levels, whereas the higher trophic positions were occupied predominantly by palaeopterygians during the Triassic, as indicated by their tendency towards larger body size. Chondrichthyans show an opposite pattern of decreasing diversity through Permian–Triassic time. We conclude that the series of events during the Permian–Triassic led to a profound change within fish communities and subsequently turned chondrichthyan-dominated faunas into osteichthyan-dominated associations typical for the Meso- and Cenozoic.