The Silveirinha Formation is an Early Eocene (Ypresian, or MP7 or Neustrian in the ELMA classification) geologic formation of the Mondego Basin in the Região Centro of central-western Portugal. The sandstones, siltstones and conglomerates were deposited in an alluvial environment.Silveirinha Formation at Fossilworks.org

The formation has provided fossils of many mammals, birds, amphibians and reptiles, as well as mollusks and ostracods, and is considered one of the richest Early Eocene faunal assemblages of Europe. The taeniodont, typically known as a North American order; Eurodon silveirinhensis and the ostracod Cypris silveirinhaensis have been named after the formation.

Description The Silveirinha Formation, named after the Silveirinha clay pit, crops out in the western part of the Mondego Basin in the Região Centro of central-western Portugal.De la Peña, 1995, p.30 The formation comprises fossiliferous lenticular calcitic conglomerates as well as laminated and cross bedded sands and brownish-red silts.

The conglomerates are interpreted as crevasse-splay deposit in a alluvial plain environment, which eventually flooded and where bogs and possibly oxbows developed, crossed by channels depending on a river system that drained higher areas more north or eastwards.

Climate

The climate in the Early Eocene was substantially warmer than today.

Paleontological significance

The Silveirinha clay pit after which the formation is named was first discovered in 1977 by Rui Pena dos Reis of Coimbra University. The unit is one of few earliest Eocene fossiliferous formations that provided a rich amphibian and reptile fauna. Most fossils were deposited in the channels after short transportation. Vegetation should have been rich in nearby areas, supporting a rich fauna. Ostracods, gastropods, amphibians and pelomedusid chelonians indicate fresh waters, although rare bivalves show that salt or at least brackish waters were not very far away.

It is hypothesized that the species D. antunesi in the genus Diacodexis was more primitive than the earliest Wasatchian D. ilicis of North America, strongly supporting a Europe to America dispersal of this genus.Godinot & De Lapparent, 2003, p.262

The formation has provided the following fossils:

Mammals Apatotherians Apatotherians reported from the Silveirinha Formation Genus Species Material Notes ImagesApatemysA. sp. IUnnamed species of apatemyidcf. A. sp. IIUnnamed species of apatemyid comparable to ApatemysHeterohyusH. sp. IUnnamed species of apatemyidH. sp. IIUnnamed species of apatemyidRussellmysR. denisaeLeft maxilla with embedded teethAn apatemyid

Bats Bats reported from the Silveirinha Formation Genus Species Material Notes ImagesArchaeonycterisA.? praecursorToothAn archaeonycterid

Cimolestans

Cimolestans reported from the Silveirinha Formation Genus Species Material Notes ImagesDidelphodusD. sp.A cimolestidIlerdoryctesI. cf. sigeiA cimolestid

Eulipotyphlans Eulipotyphlans reported from the Silveirinha Formation Genus Species Material Notes ImagesDormaalidae indet.IndeterminateReported as a dormaalid (a now invalid term synonymous with Amphilemuridae)LeptacodonL. nascimentoiA nyctitheriidcf. L. sp.A nyctitheriidNyctitheriidae indet.IndeterminateRemains of an undetermined nyctitheriidTalpavus?T. sp.Am erinaceomorph

Ferae Ferae reported from the Silveirinha Formation Genus Species Material Notes ImagesCreodonta indet.IndeterminateReported as a creodont (a now obsolete group consisting of oxyaenids and hyaenodonts)DormaalocyonD. cf. latouriA carnivoramorph, originally reported as a species of MiacisMiacidae indet.IndeterminateA carnivoramorphMiacisM. cf. latouriReassigned to the genus Dormaalocyoncf. M. sp.A carnivoramorphViverravuscf. V. sp.A viverravid

Metatherians Metatherians reported from the Silveirinha Formation Genus Species Material Notes ImagesPeratheriumP. cf. constansA herpetotheriid

Primatomorphs Primatomorphs reported from the Silveirinha Formation Genus Species Material Notes ImagesArciusA. zbyszewskiiTeethA paromomyidCantiuscf. C. sp.An adapiformDonrusselliaD. lusitanicaTeethAn adapiform

Rodents Rodents reported from the Silveirinha Formation Genus Species Material Notes ImagesCorbarimysC. paisiTeethAn ischyromyid, originally reported as a species of MicroparamysEuromysE. cardosoiJaw fragment and teethAn ischyromyidMeldimysM. cardosoiJaw fragment and teethReassigned to the genus EuromysMicroparamysM. paisiTeethReassigned to the genus CorbarimysM. cf. nanusAn ischyromyid

Taeniodonts Taeniodonts reported from the Silveirinha Formation Genus Species Material Notes ImagesEurodonE. silveirinhensisTeethA conoryctid

Ungulates Ungulates reported from the Silveirinha Formation Genus Species Material Notes ImagesDiacodexisD. antunesiTeeth and an astragalusA diacodexeidHyracotheriumH. cf. vulpicepsSpecies reassigned to the genus PliolophusLophiaspisL. mauretteiDeciduous premolar toothA lophiodontidMicrohyusM. reisi446 teeth, 4 astragali and 9 calcaneiGenus renamed as TeilhardimysMondegodonM. eutrigonusTeethA mesonychianPaschatheriumP. marianaeTeethA hyopsodontidPliolophusP. cf. vulpicepsAn equid, originally reported as a species of HyracotheriumTeilhardimysT. reisi446 teeth, 4 astragali and 9 calcaneiA hyopsodontid, originally reported under the name Microhyus reisi

Reptiles Birds Birds reported from the Silveirinha Formation Genus Species Material Notes ImagesFluviatilavisF. antunesiLeg bonesA recurvirostridNeornithes indet.IndeterminateRemains of an undetermined small bird

Crocodilians Crocodilians reported from the Silveirinha Formation Genus Species Material Notes ImagesDiplocynodonD. sp.Isolated bones and teethAn eusuchian

Squamates Squamates reported from the Silveirinha Formation Genus Species Material Notes ImagesAmphisbaenidae indet.Indeterminate2 jaw fragments and about 10 trunk vertebraeA worm lizardAnguinae indet.Indeterminate A partial jaw bone and a trunk vertebraAn anguid lizardBoidae indet.Indeterminate16 trunk vertebraeA boaDunnophisD. matronensis34 trunk vertebraeA dwarf boaGeiseltaliellusG. sp.Posterior part of the maxillaA casquehead lizardGekkonidae indet.IndeterminateTwo jaw fragments and a trunk vertebraA geckoGlyptosaurinae indet.IndeterminateIncomplete jaw bones and hundreds of osteodermsA glyptosaurineGlyptosaurini indet.IndeterminateSkull fragments and isolated osteodermsA glyptosaurineIguanidae indet.Indeterminate3 bone fragments with teethAn iguanidMelanosaurini indet.IndeterminateAn incomplete parietalA glyptosaurineMelanosauruscf. M. sp.An incomplete jugal and a fragmentary skull bone (probably a parietal)A glyptosaurineScincomorpha indet.Indeterminate genus 14 bone fragments with teethA scincomorph lizardIndeterminate genus 2A bone fragment with 2 teeth and a trunk vertebraA scincomorph lizardSerpentes indet.IndeterminateA trunk vertebraA non-boa snakeTinosauruscf. T. sp.Bone fragment with 2 teethAn agamidVaranidae indet.IndeterminateA trunk vertebraA monitor lizard

Turtles Turtles reported from the Silveirinha Formation Genus Species Material Notes ImagesNeochelysN. sp.Isolated fragmentsA side-necked turtle

Amphibians Amphibians reported from the Silveirinha Formation Genus Species Material Notes ImagesPelobatidae indet.Indeterminate2 ilium fragmentsA European spadefoot toadSalamandridae indet.IndeterminateVertebrae and humerus fragmentsA salamander

Fish Fish reported from the Silveirinha Formation Genus Species Material Notes ImagesEgertoniaE. sp.A bonefishPercichthyidae indet.IndeterminateA temperate perch

Invertebrates Arthropods Arthropods reported from the Silveirinha Formation Genus Species Material Notes ImagesCyclocyprisC.? sp.An ostracodCypriaC.? sp.An ostracodCypridacea indet.Indet. sp. 1An ostracod, outline similar to that of Hebeina ovataIndet. sp. 2An ostracodIndet. sp. 3An ostracod, morphologically similar to EucyprisIndet. sp. 4An ostracod, morphologically similar to EucyprisCyprisC. silveirinhaensis12 carapacesAn ostracodIlyocyprisI. lusitanicus5 carapacesAn ostracodLepidoptera indet.IndeterminateColeophoreCase of a moth

Molluscs Molluscs reported from the Silveirinha Formation Genus Species Material Notes ImagesBithyniaB. soaresiShells and operculaA freshwater snailCardiacea indet.IndeterminateSmall valve fragmentA cockleChlamysC. sp.Valve fragmentA scallopGyraulusG. antunesiShell fragments and internal mouldsA freshwater snail

Plants Plants reported from the Silveirinha Formation Genus Species Material Notes ImagesDicotyledoneae indet.IndeterminateSeedsFossil seeds of several types of dicotsGymnospermae indet.IndeterminateAmberResin of an undetermined gymnospermNitellopsisN. (Tectochara) dutempleiLarge numbers of gyrogonitesA green algaVitisV. sp.A grapevine

See also

List of fossiliferous stratigraphic units in Portugal Nanjemoy Formation, contemporaneous fossiliferous formation of the eastern United States Wasatch Formation, contemporaneous fossiliferous formation of the western United States Itaboraí Formation, contemporaneous fossiliferous formation of eastern Brazil

References

Bibliography