scholarly journals The southernmost occurrence of <i>Ichthyosaurus</i> from the Sinemurian of Portugal

Fossil Record ◽  
2021 ◽  
Vol 24 (2) ◽  
pp. 287-294
Author(s):  
João Sousa ◽  
Octávio Mateus
Keyword(s):  
West Coast ◽  
Fossil Record ◽  
Geographical Range ◽  
Lusitanian Basin

Abstract. The ichthyosaur fossil record of Portugal is composed of specimens from the localities of São Pedro de Moel, Alhadas, Cadima, Murtede, Casal do Combo, Condeixa, Alvaiázere and Tomar, within the confines of the Lusitanian Basin, ranging in age from the Sinemurian to the Aalenian. We reviewed the historical ichthyosaur finds in Portugal, and in this work we focus on the specimen IST-MDT 85, from the Sinemurian of Praia de Nossa Senhora da Vitória, central west coast of Portugal. The specimen was herein ascribed to Ichthyosaurus cf. communis, based on characters of the humerus in comparison with other specimens. This is the southernmost documented occurrence of Ichthyosaurus, widening the geographical range of the genus.

scholarly journals How predictable is extinction? Forecasting species survival at million-year timescales

2019 ◽  
Vol 374 (1788) ◽  
pp. 20190392 ◽  
Author(s):  
Peter Smits ◽  
Seth Finnegan
Keyword(s):  
Fossil Record ◽  
Human Impacts ◽  
Rank Order ◽  
Extinction Risk ◽  
Geographical Range ◽  
The Past ◽  
The Future ◽  
Out Of Sample ◽  
Extinction Events ◽  
Over Time

A tenet of conservation palaeobiology is that knowledge of past extinction patterns can help us to better predict future extinctions. Although the future is unobservable, we can test the strength of this proposition by asking how well models conditioned on past observations would have predicted subsequent extinction events at different points in the geological past. To answer this question, we analyse the well-sampled fossil record of Cenozoic planktonic microfossil taxa (Foramanifera, Radiolaria, diatoms and calcareous nanoplankton). We examine how extinction probability varies over time as a function of species age, time of observation, current geographical range, change in geographical range, climate state and change in climate state. Our models have a 70–80% probability of correctly forecasting the rank order of extinction risk for a random out-of-sample species pair, implying that determinants of extinction risk have varied only modestly through time. We find that models which include either historical covariates or account for variation in covariate effects over time yield equivalent forecasts, but a model including both is overfit and yields biased forecasts. An important caveat is that human impacts may substantially disrupt range-risk dynamics so that the future will be less predictable than it has been in the past. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’

scholarly journals First spinosaurid dinosaur from Australia and the cosmopolitanism of Cretaceous dinosaur faunas

2011 ◽  
Vol 7 (6) ◽  
pp. 933-936 ◽  
Author(s):  
Paul M. Barrett ◽  
Roger B. J. Benson ◽  
Thomas H. Rich ◽  
Patricia Vickers-Rich
Keyword(s):  
Early Cretaceous ◽  
Fossil Record ◽  
Cervical Vertebra ◽  
Global Distribution ◽  
Geographical Range ◽  
Theropod Dinosaur

A cervical vertebra from the Early Cretaceous of Victoria represents the first Australian spinosaurid theropod dinosaur. This discovery significantly extends the geographical range of spinosaurids, suggesting that the clade obtained a near-global distribution before the onset of Pangaean fragmentation. The combined presence of spinosaurid, neovenatorid, tyrannosauroid and dromaeosaurid theropods in the Australian Cretaceous undermines previous suggestions that the dinosaur fauna of this region was either largely endemic or predominantly ‘Gondwanan’ in composition. Many lineages are well-represented in both Laurasia and Gondwana, and these observations suggest that Early–‘middle’ Cretaceous theropod clades possessed more cosmopolitan distributions than assumed previously, and that caution is necessary when attempting to establish palaeobiogeographic patterns on the basis of a patchily distributed fossil record.

scholarly journals Shark–seal interaction off South Africa’s west coast during the early Pliocene (5 Ma)

2021 ◽  
Vol 117 (3/4) ◽  
Author(s):  
Romala Govender
Keyword(s):  
West Coast ◽  
Fossil Record ◽  
Feeding Behaviour ◽  
Marine Mammals ◽  
Early Pliocene ◽  
Geological Past ◽  
Tooth Marks

A study of the Mio-Pliocene marine palaeoenvironment on South Africa’s west coast revealed aspects of the biology and behaviour of fossil marine mammals. Close examination showed that seals from Langebaanweg suffered from pathologies and bore marks of marine carnivore activity. This study adds to our knowledge of shark feeding behaviour in the geological past and is one of a few studies of sharks feeding on seals in the fossil record. Two incomplete seal humeri with shark tooth marks are the first documented evidence from South Africa’s Mio-Pliocene of such behaviour. These injuries show no healing, which suggests that the animals were most likely scavenged.

scholarly journals The impact of the Toarcian Oceanic Anoxic Event (T-OAE) on the radiation of Early Jurassic dinoflagellate cysts in the Lusitanian Basin, Portugal

2019 ◽  
Author(s):  
Vânia Fraguito Correia ◽  
James B. Riding ◽  
Luís V. Duarte ◽  
Paulo Fernandes ◽  
Zélia Pereira
Keyword(s):  
Fossil Record ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Dinoflagellate Cysts ◽  
Dinoflagellate Cyst ◽  
Oceanic Anoxic Event ◽  
Eukaryotic Phytoplankton ◽  
The Family ◽  
The Impact ◽  
Lusitanian Basin

Dinoflagellates, together with diatoms and coccolithophores, form a major element of the marine eukaryotic phytoplankton, and are significant primary producers. Based on the fossil record, dinoflagellates appeared in Middle Triassic and during the Early Jurassic (late Pliensbachian) and underwent an important evolutionary radiation episode, with the occurrence of around 40 new species. The Lower Jurassic is particularly well-developed in the Lusitanian Basin of central western Portugal. This depocentre is filled mainly with marine Jurassic sediments, characterized by marl-limestone alternations. We analysed 214 samples from six Lower Jurassic sections in the Lusitanian Basin. The Pliensbachian–Toarcian succession in the Lusitanian Basin is characterised by relatively low dinoflagellate cyst diversity. Only fifteen taxa were recorded; these are assigned to seven genera. These are Luehndea, Mancodinium, Mendicodinium, Nannoceratopsis, Scriniocassis, Sentusidinium and Valvaeodinium. At the base of upper Pliensbachian (Amaltheus margaritatus ammonite biozone) the first dinoflagellate cyst appearances in the Lusitanian Basin are recorded, corresponding to the late Pliensbachian radiation event of this group. We identified the inceptions of Mancodinium semitabulatum, Luehndea spinosa, which belong to the family Mancodiniaceae, Nannoceratopsis gracilis and Nannoceratopsis senex, representing the family Nannoceratopsiaceae are also present. This family is confined to the Jurassic and the genus Nannoceratopsis is the only representative. These taxa became very common and abundant throughout the remaining late Pliensbachian and early Toarcian (Dactylioceras polymorphum ammonite biozone), before the T-OAE. The T-OAE in the Lusitanian Basin is expressed at the base of Hildaites levisoni ammonite biozone and is characterised by the apparent extinction of Luehndea spinosa and the disappearance of all dinoflagellate cyst taxa. During the remaining Toarcian only four new genera and families were identified and the abundance of this group is consistently very low. Apparently, the palaeoenvironmental changes associated with the T-OAE were more extensive in the Lusitanian Basin, compared with coeval basins in northern Europe. Hence, the T-OAE in this basin strongly affected the dinoflagellate cyst evolution patterns. Nevertheless, the late Toarcian of the Lusitanian Basin included an important evolutionary episode, namely the emergence of the first Gonyaulacaceae, due to the appearance of Sentusidinium. The family Gonyaulacaceae continued their diversification and became the most abundant family of cyst-forming dinoflagellates in the fossil record. In conclusion, the late Pliensbachian radiation of dinoflagellate cysts is well documented in the Lusitanian Basin and the T-OAE drastically affected the morphological experimentation period of this group during the remaining Early Jurassic.

scholarly journals Developmental mode influences diversification in ascidians

2013 ◽  
Vol 9 (3) ◽  
pp. 20130068 ◽  
Author(s):  
Max E. Maliska ◽  
Matthew W. Pennell ◽  
Billie J. Swalla
Keyword(s):  
Larval Development ◽  
Posterior Distribution ◽  
Fossil Record ◽  
Sea Urchins ◽  
Geographical Range ◽  
Speciation Rate ◽  
Developmental Mode ◽  
Ascidian Species ◽  
Speciation Rates

Ascidian species (Tunicata: Ascidiacea) usually have tailed, hatching tadpole larvae. In several lineages, species have evolved larvae that completely lack any tail tissues and are unable to disperse actively. Some tailless species hatch, but some do not hatch before going through metamorphosis. We show here that ascidian species with the highest speciation rates are those with the largest range sizes and tailed hatching larval development. We use methods for examining diversification in binary characters across a posterior distribution of trees, and show that mode of larval development predicts geographical range sizes. Conversely, we find that species with the least dispersive larval development (tailless, non-hatching) have the lowest speciation rates and smallest geographical ranges. Our speciation rate results are contrary to findings from sea urchins and snails examined in the fossil record, and further work is necessary to reconcile these disparate results.

scholarly journals The impact of the Toarcian Oceanic Anoxic Event (T-OAE) on the radiation of Early Jurassic dinoflagellate cysts in the Lusitanian Basin, Portugal

2019 ◽  
Author(s):  
Vânia Fraguito Correia ◽  
James B. Riding ◽  
Luís V. Duarte ◽  
Paulo Fernandes ◽  
Zélia Pereira
Keyword(s):  
Fossil Record ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Dinoflagellate Cysts ◽  
Dinoflagellate Cyst ◽  
Oceanic Anoxic Event ◽  
Eukaryotic Phytoplankton ◽  
The Family ◽  
The Impact ◽  
Lusitanian Basin

Dinoflagellates, together with diatoms and coccolithophores, form a major element of the marine eukaryotic phytoplankton, and are significant primary producers. Based on the fossil record, dinoflagellates appeared in Middle Triassic and during the Early Jurassic (late Pliensbachian) and underwent an important evolutionary radiation episode, with the occurrence of around 40 new species. The Lower Jurassic is particularly well-developed in the Lusitanian Basin of central western Portugal. This depocentre is filled mainly with marine Jurassic sediments, characterized by marl-limestone alternations. We analysed 214 samples from six Lower Jurassic sections in the Lusitanian Basin. The Pliensbachian–Toarcian succession in the Lusitanian Basin is characterised by relatively low dinoflagellate cyst diversity. Only fifteen taxa were recorded; these are assigned to seven genera. These are Luehndea, Mancodinium, Mendicodinium, Nannoceratopsis, Scriniocassis, Sentusidinium and Valvaeodinium. At the base of upper Pliensbachian (Amaltheus margaritatus ammonite biozone) the first dinoflagellate cyst appearances in the Lusitanian Basin are recorded, corresponding to the late Pliensbachian radiation event of this group. We identified the inceptions of Mancodinium semitabulatum, Luehndea spinosa, which belong to the family Mancodiniaceae, Nannoceratopsis gracilis and Nannoceratopsis senex, representing the family Nannoceratopsiaceae are also present. This family is confined to the Jurassic and the genus Nannoceratopsis is the only representative. These taxa became very common and abundant throughout the remaining late Pliensbachian and early Toarcian (Dactylioceras polymorphum ammonite biozone), before the T-OAE. The T-OAE in the Lusitanian Basin is expressed at the base of Hildaites levisoni ammonite biozone and is characterised by the apparent extinction of Luehndea spinosa and the disappearance of all dinoflagellate cyst taxa. During the remaining Toarcian only four new genera and families were identified and the abundance of this group is consistently very low. Apparently, the palaeoenvironmental changes associated with the T-OAE were more extensive in the Lusitanian Basin, compared with coeval basins in northern Europe. Hence, the T-OAE in this basin strongly affected the dinoflagellate cyst evolution patterns. Nevertheless, the late Toarcian of the Lusitanian Basin included an important evolutionary episode, namely the emergence of the first Gonyaulacaceae, due to the appearance of Sentusidinium. The family Gonyaulacaceae continued their diversification and became the most abundant family of cyst-forming dinoflagellates in the fossil record. In conclusion, the late Pliensbachian radiation of dinoflagellate cysts is well documented in the Lusitanian Basin and the T-OAE drastically affected the morphological experimentation period of this group during the remaining Early Jurassic.

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