Dactylosaurus
Encyclopedia
Dactylosaurus is a genus
of nothosaur
in the family
Pachypleurosauridae. Along with Anarosaurus
, Dactylosaurus was one of the earliest known pachypleurosaurs to come from Europe
.
" and sauros (σαυρος), meaning "lizard
" or "reptile
."
-shaped. There are 17 cervical
vertebrae and the cervical rib
s have anterior processes. The maxilla
e of Dactylosaurus extended broadly up the side of the snout.
specimen (MGUWR WR 3871s) of D. gracilis was only a partial skeleton
, consisting of the anterior end alone. Because it differed slightly from the fossils of D. gracilis, it was first thought to belong to the species D. schroederi, which is now considered a junior synonym for juvenile D. gracilis. Once this was established, the juvenile fossil, which was found before the adult fossils, became the holotype. The one limb
that was found (a left forelimb), was noted to have a slimmer radius
and ulna
than Neusticosaurus, a similar nothosaur from Europe
. D. gracilis is the smallest known species in its family, which includes the much more recognized Keichousaurus
, a nothosaur often remembered for its small size. The original holotype of D. gracilis is considered a juvenile, however the size of a nothosaur when its bone
s harden is used to show size, making the estimate as smallest member of its family still valid.
Dactylosaurus lived in the Middle Triassic period during the Anisian
faunal stage
, of central Europe. In terms of geology
, they are found in the lowest Muschelkalk
layers, in and around the Gogolin Formation.
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 nothosaur
Nothosaur
Nothosaurs were Triassic marine sauropterygian reptiles that may have lived like seals of today, catching food in water but coming ashore on rocks and beaches. They averaged about in length, with a long body and tail. The feet were paddle-like, and are known to have been webbed in life, to help...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Pachypleurosauridae. Along with Anarosaurus
Anarosaurus
Anarosaurus is an extinct genus of early plesiosaur that lived in the Middle Triassic period ....
, Dactylosaurus was one of the earliest known pachypleurosaurs to come from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
.
Etymology
Dactylosaurus comes from the Greek daktulos (δακτυλος), "fingerFinger
A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....
" and sauros (σαυρος), meaning "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...
" or "reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
."
Description
The nasal bones of Dactylosaurus meet and are broadly structured. The upper temporal fenestra is large and kidneyKidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
-shaped. There are 17 cervical
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...
vertebrae and the cervical rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...
s have anterior processes. The maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
e of Dactylosaurus extended broadly up the side of the snout.
D. gracilis
The holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen (MGUWR WR 3871s) of D. gracilis was only a partial skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
, consisting of the anterior end alone. Because it differed slightly from the fossils of D. gracilis, it was first thought to belong to the species D. schroederi, which is now considered a junior synonym for juvenile D. gracilis. Once this was established, the juvenile fossil, which was found before the adult fossils, became the holotype. The one limb
Limb (anatomy)
A limb is a jointed, or prehensile , appendage of the human or other animal body....
that was found (a left forelimb), was noted to have a slimmer radius
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
and ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
than Neusticosaurus, a similar nothosaur from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. D. gracilis is the smallest known species in its family, which includes the much more recognized Keichousaurus
Keichousaurus
Keichousaurus is a genus of marine reptile in the pachypleurosaur family which went extinct at the close of the Triassic in the Triassic-Jurassic extinction event. The name derives from Kweichow in China where the first fossil specimen was discovered in 1957...
, a nothosaur often remembered for its small size. The original holotype of D. gracilis is considered a juvenile, however the size of a nothosaur when its bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
s harden is used to show size, making the estimate as smallest member of its family still valid.
Distribution
Anisian
In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 245 million years ago until 237 million years ago, approximately...
faunal stage
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
, of central Europe. In terms of geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
, they are found in the lowest Muschelkalk
Muschelkalk
The Muschelkalk is a sequence of sedimentary rock strata in the geology of central and western Europe. It has a Middle Triassic age and forms the middle part of the Germanic Trias, that further consists of the Buntsandstein and Keuper...
layers, in and around the Gogolin Formation.
External links
- Pachypleurosauridae from Palaeos.com (technical)
- Dactylosaurus from the Plesiosaur Directory