Lisboasaurus
Encyclopedia
Lisboasaurus is a small (400 mm length) genus
of Mesozoic
crocodylomorph that lived in fresh water. It is known from fossilized tooth and jaw fragments of Late Jurassic and Early Cretaceous age. Two species have been described. In the past Lisboasaurus has been interpreted as a Mid Jurassic avialan
, troodontid, or an anguimorph lizard
. Both species are currently assigned to Crocodylomorpha
, one is reassigned to the genus Lusitanisuchus
.
In the 1960s paleontologists From the Free University Berlin located new vertebrate fossil sites that included the lignite mines of Guimarota, near the town of Leiria, Portugal. These lignites are dated by Milner
and Evans
, 1991, between Bathonian
(middle Jurassic) to Oxfordian
(early Late Jurassic
) age. Schwarz
and Fechner
, 2004, date them as Late Jurassic
.
Seiffert, (1970, 1973), described Lisboasaurus as a genus of anguimorph lepidosaur comprising two species, L. estesi and L. mitracostatus. He subdivided the latter species into two subspecies in the first paper, but not in the second paper. In 1983 Estes
listed the material as Lacertilia incertae sedis
. Milner and Evans, 1991, redescribed L. estesi as a maniraptoran and, more specifically, as an early avialan or troodontid They also cast doubt on the identification of the more poorly preserved L. mistracostatus, considering it a nomen dubium. Buscalioni and Evans et al. revised this assignment by demonstrating that the material referred to L. estesi was closely allied with an Early Cretaceous crocodylomorph (LH 7991) from Las Hoyas, Spain
. Buscalioni and Evans supported the nomen dubium status of L. mistracostatus. However, Schwarz and Fechner, 2004, demonstrated that the material referred to L. mistracostatus is identical to teeth and fragments found in Porto Dinheiro, and new cranial and mandibular material collected from Guimarota between 1973 and 1982. They referred all L. mistracostatus specimens to a new genus they erected, Lusitanisuchus, creating the new name Lusitanisuchus mistracostatus.
Schwarz and Fechner (2008) described a new dentary from the Uña coal mine of Cuenca province, Spain. Its teeth demonstrate that it belongs to Lisboasaurus. This dentary was the first Lisboasaurus fossil from the Barremian
age of the Early Cretaceous. The new data extracted from the dentary make it more certain that Lisboasaurus was a neosuchia
n crocodylomorph.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
crocodylomorph that lived in fresh water. It is known from fossilized tooth and jaw fragments of Late Jurassic and Early Cretaceous age. Two species have been described. In the past Lisboasaurus has been interpreted as a Mid Jurassic avialan
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
, troodontid, or an anguimorph lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
. Both species are currently assigned to Crocodylomorpha
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
, one is reassigned to the genus Lusitanisuchus
Lusitanisuchus
Lusitanisuchus is an extinct genus of mesoeucrocodylian crocodylomorph. Mostly fragmentary fossils have been found from several localities in Portugal and are Late Jurassic and Early Cretaceous in age....
.
In the 1960s paleontologists From the Free University Berlin located new vertebrate fossil sites that included the lignite mines of Guimarota, near the town of Leiria, Portugal. These lignites are dated by Milner
Milner
-People:* Alfred Milner, 1st Viscount Milner , British colonial administrator* Andy Milner , English footballer* Brenda Milner , English-Canadian neuropsychologist* Eric Milner-White , English cleric...
and Evans
Evans
Evans may refer to:people*Evans *for a particular person with the surname, see the List of people with surname Evans.place*Evans, California in the United States*Evans, Colorado in the United States*Evans, Georgia in the United States...
, 1991, between Bathonian
Bathonian
In the geologic timescale the Bathonian is an age or stage of the Middle Jurassic. It lasted from approximately 167.7 Ma to around 164.7 Ma...
(middle Jurassic) to Oxfordian
Oxfordian stage
The Oxfordian is, in the ICS' geologic timescale, the earliest age of the Late Jurassic epoch, or the lowest stage of the Upper Jurassic series. It spans the time between 161.2 ± 4 Ma and 155.7 ± 4 Ma...
(early Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
) age. Schwarz
Schwarz
Schwarz is a common surname, derived from the German , , meaning the color black. It may refer to:-People:*Alan Schwarz , American writer*Albert Schwarz, Russian-born American theoretical*Annette Schwarz, German pornographic actress...
and Fechner
Fechner
Fechner is a surname of:* Christian Fechner , a French film producer and screenwriter* Gustav Fechner , a German experimental psychologist* Harry Fechner , a German football defender...
, 2004, date them as Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
.
Seiffert, (1970, 1973), described Lisboasaurus as a genus of anguimorph lepidosaur comprising two species, L. estesi and L. mitracostatus. He subdivided the latter species into two subspecies in the first paper, but not in the second paper. In 1983 Estes
Estes
Estes is a popular surname derived from the House of Este. It is also said to derive from Old English and have the meaning "of the East." As a surname, it has been traced to southern England in the region of Kent, as early as the mid-16th century....
listed the material as Lacertilia incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
. Milner and Evans, 1991, redescribed L. estesi as a maniraptoran and, more specifically, as an early avialan or troodontid They also cast doubt on the identification of the more poorly preserved L. mistracostatus, considering it a nomen dubium. Buscalioni and Evans et al. revised this assignment by demonstrating that the material referred to L. estesi was closely allied with an Early Cretaceous crocodylomorph (LH 7991) from Las Hoyas, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
. Buscalioni and Evans supported the nomen dubium status of L. mistracostatus. However, Schwarz and Fechner, 2004, demonstrated that the material referred to L. mistracostatus is identical to teeth and fragments found in Porto Dinheiro, and new cranial and mandibular material collected from Guimarota between 1973 and 1982. They referred all L. mistracostatus specimens to a new genus they erected, Lusitanisuchus, creating the new name Lusitanisuchus mistracostatus.
Schwarz and Fechner (2008) described a new dentary from the Uña coal mine of Cuenca province, Spain. Its teeth demonstrate that it belongs to Lisboasaurus. This dentary was the first Lisboasaurus fossil from the Barremian
Barremian
The Barremian is an age in the geologic timescale between 130.0 ± 1.5 Ma and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch...
age of the Early Cretaceous. The new data extracted from the dentary make it more certain that Lisboasaurus was a neosuchia
Neosuchia
Neosuchia is an unranked clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to Crocodylus niloticus than to Notosuchus terrestris...
n crocodylomorph.