During the Late Cretaceous high sea levels split Europe up into a series of islands, each with its own distinctive fauna, with fossils from different parts of Europe show affinities to those from other continents, notably Asia, North America and Gondwana (Africa & South America). In recent years larger fossil vertebrates, such as Dinosaurs, Pterosaurs, Crocodiles and Turtles, have been extensively studied in Iberia, but less attention has been paid to smaller vertebrates, which are often important when trying to assess connections between faunas of different regions.
In a paper published in the journal Cretaceous Research on 30 July 2015, Alejandro Blanco and Arnau Bolet of the Institut Catalàde Paleontologia Miquel Crusafont at the Universitat Autònomade Barcelona, Hugues-Alexandre Blain of the Institut Catalàde Paleoecologia Humana i EvoluciòSocial and the Area de Prehistòria at the Universitat Rovira i Virgili, and Víctor Fondevilla of the Departament de Geologia (Estratigrafia) at the Universitat Autònoma de Barcelona describe a series of fossils of smaller vertebrates from four exposures of the Late Cretaceous Tremp Formation of northeastern Spain. The Tremp Formation comprises a series of beds laid down on a floodplain with a meandering or braded river, occasional isolated lakes and marine influences in places.
The first fossils examined dome from the Serrat del Rostiar-1 locality, where the exposure composes grey mudstones with pedogenic nodules which represent portions of fossilized soil, thought to have formed on the floodplain close to a meandering river (represented by sandstone deposits).
This site has produced a partial frontal bone (part of the skull) and three humerus fragments assigned to an unknown Albanerpetontid, an extinct group of Salamander-like Lisamphibians with bony scales, known from the Middle Jurassic to the End Pliocene of Europe, North America and (in one case) Morocco, and which have previously been recorded from several sites in Iberia.
Albanerpetontid Lisamphibians from Serrat del Rostiar-1. (A) Frontal in dorsal view. (B) Proximal and (C) distal epiphyses of humeri in ventral view. Blanco et al. (2015).
This site also produced a fragment of right and two left illia, a partial scapula, a fragment of humerus and one whole and one partial vertebrae assigned to an unknown Painted Frog, Discoglossinae, a group of Frogs found today in southern Europe, North Africa and Israel. The earliest known fossil assigned to this group comes from the Jurassic of Spain, and Cretaceous specimens have previously been described from Spain, Romania and Wyoming. The site also produced one fragment of ilium assigned to an unknown Alytine Frog (Midwife Toad).
Alytid Anurans from Serrat del Rostiar-1. (A) Right ilium in lateral view. (B) Left ilium in lateral view. (C) Left ilium in lateral view. (D) Left scapula in lateral view. (E) Sacral and (F) trunk vertebrae in ventral view. (G) Alytinae: right ilium in lateral view. Blanco et al. (2015).
In addition a fragment of ilium and a partial vertebrae assigned to an unknown Palaeobatrachid Frog were found at this site. Palaeobatrachid Frogs are well documented from the Eocene-Pliocene of Europe, with a few fragmentary specimens from Spain and North America.
Palaeobatrachid Anurans from Serrat del Rostiar-1. (A) Left ilium in lateral view. (B) Trunk vertebra in ventral view. Blanco et al. (2015).
Serrat del Rostiar-1 also produced fragment of an urostyle, the epiphysis of a radioulna, two partial vertebrae and some tibiofibular and radioulnar fragments assigned to unknown Frogs.
Indeterminate Anurans from Serrat del Rostiar-1. (A) Radioulna in lateral view. (B) Urostyle in dorsal view. Blanco et al. (2015).
Also from Serrat del Rostiar-1 is a frontal bone tentatively assigned to a Gecko. Geckos are well known in the Cretaceous in Asia, but otherwise more-or-less unknown, However this Serrat del Rostiar-1 specimen closely resembles another possible Gecko specimen from the Cretaceous of Romania, suggesting a possible unknown lineage of European Cretaceous Geckos.
Frontal of an indeterminate ?Gekkota from Serrat del Rostiar-1 in ventral view. Blanco et al. (2015).
The Serrat del Rostiar-1 site also produced three tooth-bearing jaw fragments tentatively assigned to ab unknown Skink. Skinks first appeared in the Jurassic and by the end of the Cretaceous appear to have been distributed across Europe, Asia and North America. In Europe they have been previously described from the Late Cretaceous of Spain, France and Romania.
Tooth-bearing bones of an indeterminate ‘Scincomorph’ Lizard from Serrat del Rostiar-1 in lingual view. Blanco et al. (2015).
This site also produced a single vertebrae of a possible Anguid (Glass) Lizard. Anguids appeared in the Late Cretaceous of North America, and while common in parts of that continent by the end of the period, are not previously known in Europe till the Cainozoic.
Vertebra of Anguidae indet. from Serrat del Rostiar-1 in dorsal (E), ventral (F) and lateral (G) view. Blanco et al. (2015).
Finally the Serrat del Rostiar-1 site produced a tooth set in a fragment of bone from an unknown Iguanid, and another tooth set in bone plus an ishium of an unknown Lizard. The oldest known Iguanid comes from the Early Jurassic of India, and the group were widespread by the End Cretaceous.
Iguanid tooth from Serrat del Rostiar-1 in lingual view. Blanco et al. (2015).
The L'Espinau site produces grey marly mudstones with organic inclusions, mostly in the form of coaly material. It has a distinctive bone-bed, which has produced numerous scattered Hadrosaur bones. The site is not close to any fluvial (river) sandstone deposits, though some lucastrine (lake) limestones are found nearby, and the site probably represents a floodplain.
L'Espinau has produced a partial premaxilla, a fragment of maxilla, five fragments of dentaries and a portion of a humerus assigned to Albanerpetontid Lisamphibians. These appear simlar to (less fragmentary) material previosuly described from the Blasi-2 locality which is nearby, and which have been assigned to the genus Albanerpeton, which is otherwise known from fluvial, lucastrine and floodplain environments in the Cretaceous of North America and Cainozoic of Europe, surviving as late as the Pliocene in Hungary and Italy.
Albanerpetontid Lisamphibians from L'Espinau. (D) Left premaxilla in lingual view. (E) ?Maxilla in lingual view. (F) Left dentary and (G) right dentary in lingual view. (H) Proximal fragment of humerus in ventral view. Blanco et al. (2015).
The L'Espinau also produced two sacral vertebrae and two partial ilia assigned to an unknown Alytine Anuran (Midwife Toad), a group closely related to the Painted Frogs, Discoglossinae. This group is also found in southern Europe and North Africa today, but which in the Cretaceous has previously been described from Central Asia and Romania.
Alytid Anurans from L'Espinau. (H) Sacral vertebra. (I) Sacral vertebra. (J) Left and (K) right ilium in lateral view. Blanco et al. (2015).
This site also yielded two partial humerii of an unknown Palaeobatrachid Frog, a fragment of maxila from either a Pelobatid (Spadefoot Toads, which are found today in North America, Europe, North Africa and western Asia, and which are known as fossils from the Jurassic and Cretaceous of Norh America and the Eocene onwards in Europe) or a Gobiatid (an extict group of Anurans known from the Cretaceous of Central Asia), and a fragmentary vertebra, a urostyle, a coracoid, a partial radioulna, a humeral epiphysis and six fragments of tibiobifulae from unknown Frogs.
Maxilla of Pelobatidae or Gobiatidae indet. from L'Espinau in lingual (C) and lateral (D) view. Blanco et al. (2015).
L'Espinau also produced a tooth from an indeterminate Iguanid Lizard in a piece of bone.
Iguanid tooth from L'Espinau in lingual view. Blanco et al. (2015).
The Serrat del Pelleu site comprises grey mudstones overlying fine ochre sandstones, probaby laid down on a quite, non-erosive part of a meandering river system. This site has previously produced numerous Turtle, Crocodylomorph and Hadrosaur specimens.
Blanco et al. describe a partial humerous of a Albanerpetontid Lisamphibian from this site, as well as one prearticular, three partial humeri and six fragments of tibiofibulae from an unknown Painted Frog.
Distal epiphysis of humerus of an unknown Painted Frog from L'Espinau in ventral view. Blanco et al. (2015).
Finally the Camí del Soldat location comprises thinly interbedded grey mudstones and fine sandstones thought to have been laid down on a quite meander-loop of a river. This location produced one urostyle and two partial vertebrae of an unknown Frog.
The Tremp paleoriver valley has yielded a diverse fauna of Lisamphibians and Lizards, much of it similar to other localities from the Late Cretaceous of Spain. However it also contains the oldest, and only Mesozoic, Midwife Toad remains known Europe to date and possibly the oldest, and only Mesozoic, Gecko from Iberia (and possibly Europe). Curiously the sites produced no Snake remains, despite the fact that Snakes are thought to have been well established globally by the Late Cretaceous, though this may be a result of taphonomic or sampling bias, given the low number of specimens in the study.
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