''Fraxinisaura'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of basal

lepidosauromorph Lepidosauromorpha (in PhyloCode known as Pan-Lepidosauria) is a group of reptiles comprising all diapsids closer to lizards than to archosaurs (which include crocodiles and birds). The only living sub-group is the Lepidosauria, which contains two ...

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

known from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. The only known species is ''Fraxinisaura rozynekae''. It possessed an elongated snout, unique features of the teeth, and an ilium (upper hip bone) which was intermediate in orientation between sphenodontians (the branch of

lepidosaurs The Lepidosauria (, from Greek meaning ''scaled lizards'') is a Order (biology), superorder or Class (biology), subclass of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata also includes Lizard, lizards and Snake, snakes. Sq ...

including the

tuatara The tuatara (''Sphenodon punctatus'') is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephal ...

) and

squamates Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles; most members of which are commonly known as lizards, with the group also including snakes. With over 11,991 species, it is also the second-largest order ...

(the branch including

lizards Lizard is the common name used for all squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The ...

). Based on characteristics of the maxilla, it is considered a close relative of ''

Marmoretta ''Marmoretta'' is an extinct genus of small lepidosauromorph reptile known from the Middle-Late Jurassic of Britain and Portugal. The genus contains two species, ''M. oxoniensis'' and ''M. drescherae''. Discovery and naming ''Marmoretta'' is k ...

'' from the

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

of the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

, resolving a

ghost lineage A ghost lineage is a hypothesized ancestor in a species lineage that has left no fossil evidence, but can still be inferred to exist or have existed because of gaps in the fossil record or genomic evidence. The process of determining a ghost line ...

between that genus and other Triassic basal lepidosauromorphs.

Discovery

Remains of ''Fraxinisaura'' have only been recovered from the Schumann limestone quarry near Vellberg, Germany. Stratigraphically, it hails from the Untere Graue Mergel Layer of the

Erfurt Formation The Erfurt Formation, also known as the Lower Keuper (German: ''Untere Keuper'', ''Lettenkeuper'', ''Lettenkohle'' or ''Lettenkohlenkeuper''), is a stratigraphic formation of the Keuper group and the Germanic Trias supergroup. It was deposited ...

, also known as the Lower Keuper. The Lower Keuper preserved a lakeshore environment of

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

(late

) age. The holotype of ''Fraxinisaura'' is SMNS 91547, a disarticulated partial skeleton encompassing portions of the skull, vertebrae, hip and limbs. Numerous other isolated bones have also been referred to the taxon. ''Fraxinisaura'' combines the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

words for lizard (''saurus'') and ash tree (''

fraxinus ''Fraxinus'' (), commonly called ash, is a genus of plants in the olive and lilac family, Oleaceae, and comprises 45–65 species of usually medium-to-large trees, most of which are deciduous trees, although some Subtropics, subtropical specie ...

''). This references the nearby village of Eschenau, which means "meadow of ash trees". The species name honors Brigette Rozynek, a fossil collector who donated many Lower Keuper fossils to local museums. ''Fraxinisaura'' was described by Rainer R. Schoch and

Hans-Dieter Sues Hans-Dieter Sues (born 1956) is a German-born American palaeontologist who is a Senior Research Geologist and Curator of Vertebrate Paleontology at the National Museum of Natural History of the Smithsonian Institution in Washington, DC. Career ...

in 2018.

Description

The skull of adults was probably 2-2.5 centimeters (.8-1 inches) in length, with a low and elongated snout. Some bones are faintly textured similar to those of kuehneosaurids. The

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

has a short facial process (upwards branch) and a uniquely long premaxillary process (front branch), conditions also known to a lesser extent in ''Marmoretta''. The 22+ maxillary teeth are characteristic as well, being conical, closely spaced, and bearing longitudinal striations at their tips. The teeth are slightly

heterodont In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals wher ...

, with those at the front of the maxilla having more recurved tips than those at the back of the maxilla, or the four at the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

. The left and right frontal and parietal bones at the top of the skull are more robust, flatter, and unfused to their counterparts in contrast to those of ''Marmoretta''. There may have been a small gap where the frontals and parietals meet. The

nasal Nasal is an adjective referring to the nose, part of human or animal anatomy. It may also be shorthand for the following uses in combination: * With reference to the human nose: ** Nasal administration, a method of pharmaceutical drug delivery * ...

bones at the top of the snout are also longer (from front-to-back) and thinner (from side-to-side) than those of ''Marmoretta''. As with most early lepidosauromorphs, the posterior process (rear branch) of the

jugal The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy ...

was very short, leaving the lower temporal fenestra open from below. Preserved postemporal bones, such as the

postorbital The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some ve ...

and

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestra ...

, were smaller and more conservative in shape than those of other early lepidosauromorphs. The rear of the

parasphenoid The parasphenoid is a bone which can be found in the cranium of many vertebrates. It is an unpaired dermal bone which lies at the midline of the roof of the mouth. In many reptiles (including birds), it fuses to the endochondral (cartilage-derived ...

had a small patch of teeth, a

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...

feature not present in most saurians. There are also three longitudinal rows of small teeth on each

pterygoid Pterygoid, from the Greek for 'winglike', may refer to: * Pterygoid bone, a bone of the palate of many vertebrates * Pterygoid processes of the sphenoid bone ** Lateral pterygoid plate ** Medial pterygoid plate * Lateral pterygoid muscle * Medial ...

bone, as well as a transverse row (which is not present in ''Marmoretta''). The ectopterygoid resembles that of ''Sphenodon'' (the modern

). The

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

has a small expansion at the tip, forming a "chin" similar to that of sphenodontians. The elongated, closely spaced dentary teeth are similar to those of the maxilla. Dentition is

pleurodont Pleurodont is a form of tooth implantation common in reptiles of the order Squamata, as well as in at least one temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 've ...

, like other basal lepidosauromorphs and lizards, but unlike sphenodontians.

Vertebrae Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

are similar to those of ''Marmoretta'' and kuehneosaurs, being amphicoelous (concave at both ends) and lacking a hole for the

notochord The notochord is an elastic, rod-like structure found in chordates. In vertebrates the notochord is an embryonic structure that disintegrates, as the vertebrae develop, to become the nucleus pulposus in the intervertebral discs of the verteb ...

. The

scapula The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

and

coracoid A coracoid is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is present as part of the scapula, but this is n ...

are fused into a

scapulocoracoid The scapulocoracoid is the unit of the pectoral girdle that contains the coracoid and scapula. The coracoid itself is a beak-shaped bone that is commonly found in most vertebrates with a few exceptions. The scapula is commonly known as the ''shoulde ...

, while the

interclavicle An interclavicle is a bone which, in most tetrapods, is located between the clavicles. Therian mammals ( marsupials and placentals) are the only tetrapods which never have an interclavicle, although some members of other groups also lack one. In ...

was large, arrow-shaped, and heavily textured. Like other lepidosauromorphs, the

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

is twisted, constricted in the middle, and possesses an

entepicondylar foramen The entepicondylar foramen is an opening in the distal (far) end of the humerus (upper arm bone) present in some mammals. It is often present in primitive placentals, such as the enigmatic Madagascan '' Plesiorycteropus''. In most Neotominae and a ...

but not an ectepicondylar one. The ilium has a distinctively long, leaf-shaped iliac blade which projects up and back at a 45 degree angle, intermediate between the horizontal iliac blade of

, and the vertical iliac blade of sphenodontians. ''

Sophineta ''Sophineta'' is an extinct genus of basal (phylogenetics), basal lepidosauromorph reptile known from the Early Triassic (late Olenekian age) of Lesser Poland Voivodeship, Małopolska Province, southern Poland. It contains a single species, ''Sop ...

'' and ''

Gephyrosaurus Gephyrosaurus is an extinct genus of lepidosaurian reptile known from the Late Triassic to Early Jurassic of the United Kingdom. It is generally considered to be one of the most primitive members of the clade Rhynchocephalia. Description ''Ge ...

'' have a similarly shaped intermediate ilium. Recovered hindlimb material generally resembles that of generalized

like ''Sphenodon'', though the

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

is somewhat more robust.

Classification

''Fraxinisaura'' does not preserve a quadrate,

sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...

, or metatarsal V, bones which are useful for determining whether a reptile is a lepidosauromorph or not. However, it does possess an entepicondylar foramen of the humerus as well as pleurodont dentition, both of which are characteristic lepidosauromorph features. The shape of the maxilla also links it to ''Marmoretta'', helping to fill the small

which lies between ''Marmoretta'' (from the mid to late

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

) and other basal lepidosauromorphs (which appeared in the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

). This classification scheme was supported by a

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

using the data matrix of

Ezcurra Ezcurra is a surname. Notable people with the surname include: * Alma Ezcurra (born 1986), Spanish politician * Bautista Ezcurra (born 1995), Argentine rugby union player * Encarnación Ezcurra (1795–1838), Argentine political activist * Exequiel ...

''et al.'' (2014). The ''Fraxinisaura'' + ''Marmoretta'' clade was tentatively considered to be closer to ''Sophineta'' and rhynchocephalians than to lizards, but lepidosauromorph relations were largely reduced into a

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tree ...

upon the addition of ''

Kuehneosaurus ''Kuehneosaurus'' is an extinct genus of Late Triassic kuehneosaurid reptile known from the Late Triassic (Norian stage) of the Penarth Group of southwest England and the Steinmergel Group of Luxembourg. Temperature at this stage and region wo ...

'' into the analysis. Adding ''Fraxinisaura'' to another lepidosauromorph analysis (

Evans Evans or Evan's may refer to: People * Evans (surname) * List of people with surname Evans * Evans Welch, Trinidad and Tobago politician Places United States * Evans Island, an island of Alaska * Evans, Colorado * Evans, Georgia * Evans County ...

and Borsuk-Białynicka (2009)) also led to a large polytomy. Below is a portion of the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

produced by adding ''Fraxinisaura'' (but not ''Kuehneosaurus'') to the analysis of Ezcurra ''et al.'' (2014):

References

{{Taxonbar, from1=Q56254434, from2=Q56254445 Lepidosauromorpha Prehistoric reptile genera Middle Triassic reptiles of Europe Fossil taxa described in 2018