Scheenstia

Scheenstia is an extinct genus of neopterygian ray-finned fish from the Late JurassicEarly Cretaceous periods. Fossils have been found in Bavaria, France, and England.

Scheenstia maximus
Life restoration of S. maximus

Scheenstia is frequently pictured as the prey of the large dinosaur Baryonyx walkeri because the scales and teeth of these fish were found in the stomach region of a fossil B. walkeri specimen. The fish remains were previously referred to the related genus Lepidotes, but all Late JurassicEarly Cretaceous species of that genus have since been re-classified as Scheenstia following detailed phylogenetic analysis.[1]

Scheenstia
Temporal range: Late JurassicEarly Cretaceous, 150–125 Ma
2013-03 Naturkundemuseum Berlin Dickschupperfisch Lepidotes maximus anagoria
Fossil specimen of S. maximus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Semionotiformes
Family: Semionotidae
Genus: Scheenstia
López-Arbarello & Sferco, 2011
Type species
Scheenstia zappi
López-Arbarello & Sferco, 2011
Species[1]

S. mantelli (Agassiz, 1833)
S. laevis (Agassiz, 1837)
S. maximus (Wagner, 1863)
S. decoratus (Wagner, 1863)
S. degenhardti (Branco, 1885)
S. hauchecornei (Wagner, 1863)
S. zappi López-Arbarello & Sferco, 2011

Classification

Scheenstia is a genus of lepisosteiform that is related to the genus Lepidotes. The latter has been one of the greatest actinopterygian wastebasket taxa, with one 2012 study finding species referrable to a minimum of three different and distantly related genera. Scheenstia is also related to Isanichthys. A cladogram showing the relations of Neopterygii was published in the review, and a simplified version labelling the previous species of Lepidotes is shown here.[1]

Ginglymodi
Semionotiformes

Sangiorgioichthys

Macrosemiidae

Luoxioingchthys

Notagogus

Macrosemius

Protopterus

Semionotidae

Semionotus

Callipurbeckiidae

Semiolepsis

Paralepidotus

Macrosemimimus

Tlayuamichin

Callipurbeckia (incl. L. minor, L. notopterus, L. tendagurensis)

Lepisoteiformes

Neosemionotus

Scheenstia (incl. L. mantelli, L. laevis, L. maximus, L. decoratus, L. degenhardti, L. hauchecorni)

Lepidotes

Isanichthys

Lepisosteoidei

References

  1. ^ a b c López-Arbarello, A. (2012). "Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii)". PLoS ONE. 7 (7): e39370. doi:10.1371/journal.pone.0039370. PMC 3394768. PMID 22808031.
Anoual Formation

The Anoual Formation is a geological formation in the High Atlas of Morocco. It is early Bathonian in age. It consists of two members. The lower member is several hundred metres thick, and consists largely of mudstone with lens beds of cross bedded sandstone, with thin intercalations of limestone that was deposited in a continental setting. The upper member is several tens of metres thick and consists of limestone deposited in a shallow marine setting. The formation is fossiliferous, with several of the limestone intercalations yielding a diverse fauna, including amphibians, reptiles, dinosaurs and mammals.

Baryonyx

Baryonyx () is a genus of theropod dinosaur which lived in the Barremian stage of the Early Cretaceous Period, about 130–125 million years ago. The first skeleton was discovered in 1983 in the Weald Clay Formation of Surrey, England, and became the holotype specimen of B. walkeri, named by palaeontologists Alan J. Charig and Angela C. Milner in 1986. The generic name, Baryonyx, means "heavy claw" and alludes to the animal's very large claw on the first finger; the specific name, walkeri, refers to its discoverer, amateur fossil collector William J. Walker. The holotype specimen is one of the most complete theropod skeletons from the UK (and remains the most complete spinosaurid), and its discovery attracted media attention. Specimens later discovered in other parts of the United Kingdom and Iberia have also been assigned to the genus.

The holotype specimen, which may not have been fully grown, was estimated to have been between 7.5 and 10 m (25 and 33 ft) long and to have weighed between 1.2 and 1.7 t (1.3 and 1.9 short tons). Baryonyx had a long, low, and narrow snout, which has been compared to that of a gharial. The tip of the snout expanded to the sides in the shape of a rosette. Behind this, the upper jaw had a notch which fitted into the lower jaw (which curved upwards in the same area). It had a triangular crest on the top of its nasal bones. Baryonyx had a large number of finely serrated, conical teeth, with the largest teeth in front. The neck formed an S-shape, and the neural spines of its dorsal vertebrae increased in height from front to back. One elongated neural spine indicates it may have had a hump or ridge along the centre of its back. It had robust forelimbs, with the eponymous first-finger claw measuring about 31 cm (12 in) long.

Now recognised as a member of the family Spinosauridae, Baryonyx's affinities were obscure when it was discovered. Some researchers have suggested that Suchosaurus cultridens is a senior synonym (being an older name), and that Suchomimus tenerensis belongs in the same genus; subsequent authors have kept them separate. Baryonyx was the first theropod dinosaur demonstrated to have been piscivorous (fish-eating), as evidenced by fish scales in the stomach region of the holotype specimen. It may also have been an active predator of larger prey and a scavenger, since it also contained bones of a juvenile Iguanodon. The creature would have caught and processed its prey primarily with its forelimbs and large claws. Baryonyx may have had semiaquatic habits, and coexisted with other theropod, ornithopod, and sauropod dinosaurs, as well as pterosaurs, crocodiles, turtles and fishes, in a fluvial environment.

Piscivore

A piscivore is a carnivorous animal that eats primarily fish. Piscivorous is equivalent to the Greek-derived word ichthyophagous. Fish were the diet of early tetrapods (amphibians); insectivory came next, then in time, reptiles added herbivory.Some animals, such as the sea lion and alligator, are not completely piscivorous, often preying on aquatic invertebrates or land animals in addition to fish, while others, such as the bulldog bat and gharial, are strictly dependent on fish for food. Humans can live on fish-based diets as can their carnivorous domesticated pets, such as dogs and cats. The name "piscivore" is derived from the Latin word for fish, piscis. Some creatures, including cnidarians, octopuses, squid, spiders, sharks, cetaceans, grizzly bears, jaguars, wolves, snakes, turtles, and sea gulls, may have fish as significant if not dominant portions of their diets.

The ecological effects of piscivores can extend to other food chains. In a study of cutthroat trout stocking, researchers found that the addition of this piscivore can have noticeable effects on non-aquatic organisms, in this case bats feeding on insects emerging from the water with the trout.There exists classifications of primary and secondary piscivores. Primary piscivores, also known as "specialists", shift to this habit in the first few months of their lives. Secondary piscivores will move to eating primarily fish later in their lifetime. It is hypothesized that the secondary piscivores' diet change is due to an adaptation to maintain efficiency in their use of energy while growing.

Semionotiformes

Semionotiformes is an order of primitive, ray-finned, primarily freshwater fish from the Triassic to the Cretaceous. The best-known genus is Semionotus of Europe and North America.

Spinosauridae

Spinosauridae (meaning "spined lizards") is a family of megalosauroidean theropod dinosaurs. The genus Spinosaurus, from which the family, subfamily, and tribe borrow their names, is the longest terrestrial predator known from the fossil record, and likely reached lengths of 15 m (49 ft). Most spinosaurids lived during the Cretaceous Period, with possible origins in the Late Jurassic, and fossils of them have been recovered worldwide, including in Africa, Europe, South America, Asia, and Australia, although none have been formally named from the latter continent. Spinosaur remains have generally been attributed to the Early to Mid Cretaceous, with the exception of the Ostafrikasaurus from the Late Jurassic.

Spinosaurids were large bipedal carnivores with elongated, crocodile-like skulls lined with conical teeth bearing little to no serrations, and small crests on top of their heads. The teeth in the front end of their lower jaws fanned out into a spoon-shaped structure similar to a rosette, which gave the animal a characteristic look. Their shoulders were robust, prominent and bore stocky forelimbs with giant "hooked" claws on the first finger of their hands. Many genera had unusually tall neural spines on their vertebrae, which supported sails or humps of skin or fat tissue.

Direct fossil evidence and anatomical adaptations indicate that spinosaurids were at least partly piscivorous, with additional fossil finds indicating they also hunted pterosaurs and small to medium-sized dinosaurs. Osteological analyses have suggested a semiaquatic lifestyle for some members of this clade.

Wessex Formation

The Wessex Formation is a fossil-rich English geological formation that dates from the Berriasian to Barremian stages (about 145–125 million years ago) of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Formation and overlies the Durlston Formation. The dominant lithology of this unit is mudstone with some interbedded sandstones.

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