Belemnotheutis

The genus Belemnotheutis is characterized by an internal shell consisting of a conical phragmocone covered apically by a thin rostrum, or guard, homologous to the bullet-shaped rostrum of true belemnites, a short forward projecting proostracum, and ten hook bearing arms of equal length. Belemnotheutis fossils are sometimes found in remarkable states of preservation, some specimens retaining permineralized soft tissue. The mantle, fins, head, arms, and hooks are well-documented from remains preserved in Lagerstätten. One specimen recovered from Christian Malford, Wiltshire and currently displayed in the Paleontology Department of the Natural History Museum in London is fossilized clasping a fish. Belemnotheutis is not a 'true' belemnite (suborder Belemnitina) but a closely related coleoid. The phragmocone of Belemnotheutis is short and blunt, measuring around to in length. The outer layer gradually thins from in thickness to only about thick at about further down the shell until it eventually disappears around the opening of the phragmocone (the peristome). Sometimes there is a hollow gap between the rostrum and the lamellar layer of the conotheca, indicating either organic content that have since disappeared or disintegration of the lamellar layer itself. The phragmocone of Belemnotheutis had about 50 chambers that were originally aragonitic, though they are usually replaced by calcium phosphate during the process of fossilization. At the very tip of the phragmocone beneath the rostrum is an embryonic shell known as the protoconch. In Belemnotheutis, like in other belemnotheutids, the protoconch is roughly cup-shaped and sealed. However, it is probably a taphonomic artefact, with the protoconch being spherical like other belemnites. The head is not well preserved in known specimens. It comprised approximately 20% of the body length (excluding the arms). Brain cartilage is observed in some specimens, as well as a pair of aragonitic statoliths which helped the animal determine horizontal orientation when swimming. Belemnotheutis, like most of the other belemnoids, had ten arms of equal length lined with two rows of inward-pointing hooks each. The length of the arms varies with the size of the individual but may have reached in larger specimens. The cross section of the exceptionally preserved body wall of a specimen from the Oxford Clay formations also reveals alternating bands of concentrically and radially oriented body fibers. They imply that Belemnotheutis were powerful swimmers and agile predators, similar to modern shallow-water squid species. The animal reached in length, including its arms. The body diameter was around 12 to 14% of the mantle length. At the center of the dorsal surface of the rostrum is a narrow V-shaped groove running about 3/5ths the length of the phragmocone from the apex, with two rounded ridges at its left and right sides. These grooves are one of the most distinctive features of the Belemnotheutidae and are theorized to have served as attachments to terminal oval or oar-shaped fins like in some modern squids. Intestinal casts (cololites) as well as the orientations and positions of fossilized remains reveal that the animal preyed on fish and other coleoids in life. Their great abundance in certain formations indicate that Belemnotheutis were highly gregarious animals, congregating in large monospecific or polyspecific shoals. ==Distribution and geological time range==

Belemnotheutis existed during the late Middle Jurassic to the Upper Jurassic epoch, from the Callovian age (166.1 to 163.5 mya) to the Kimmeridgian age (157.3 to 152.1 mya). The belemnotheutid Acanthoteuthis, a close relative which is treated by some paleontologists as synonymous with Belemnotheutis, is known to have existed from as early as the Callovian age (166.1 to 163.5 mya) of the Middle Jurassic epoch to as late as the Aptian age (125 to 112 mya) of the Lower Cretaceous epoch. The earliest known possible remains of belemnotheutids (genera Chitinobelus and Chondroteuthis) come from the Lower Jurassic, from phragmocones and rostra recovered from Toarcian formations in Dumbleton, Gloucestershire, and Ilminster, Somerset, England. However, these remains seem to have possessed the typical calcitic rostra of true belemnites rather than the characteristic aragonitic rostra of belemnotheutids. Belemnotheutis serve as index fossils. They are mostly found in Jurassic formations like the Kimmeridge Clay formation, the Oxford Clay formation, Their geographic range, thus far, is confined to Europe. ==Taxonomy and nomenclature==

Belemnotheutis are coleoids belonging to the family Belemnotheutidae. Belemnotheutis and other belemnotheutids are considered by some paleontologists to be distinct from true belemnites (suborder Belemnitina). Most authorities like Jeletzky (1966), classify it under Belemnitida in the suborder Belemnotheutina (the classification used by this article). Others like Donovan (1977) and Engeser and Reitner (1981) classify it as a distinct order, Belemnotheutida, based on the aragonitic constitution of the rostra, ==Species==

The following is a list of species described under the genus Belemnotheutis. • Belemnotheutis antiquus Pearce, 1842 • Belemnotheutis polonica Makowski, 1952 • Belemnotheutis mayri Engeser & Reitner, 1981 Belemnotheutis montefiorei has been transferred to the genus Phragmoteuthis and B. rosenkrantzi to the genus Groenlandibelus. ==Fossil ink==

Fossilized ink sacs were first discovered in belemnites in 1826 by Mary Anning a famous British fossil collector and paleontologist, who along with her brother Joseph and a friend and fellow fossil collector Elizabeth Philpot succeeded in recovering the ink, used to illustrate ichthyosaur and pterosaur fossils. The ink recovered from such fossils were also used to draw fossil ichthyosaurs by Henry De la Beche, a friend and supporter of Mary Anning. In 2008, an excavation team led by the British Geological Survey in Christian Malford recovered fossilized ink sacs from several remarkably preserved remains of Belemnotheutis antiquus in the Oxford Clay that had been previously identified during the 1840s. By mixing it with ammonia solution, the team was able to return the ink to its liquid form. Bringing to mind the 19th century practices of the aforementioned early paleontologists, they used the ~150 million year old ink to draw a replica of the original illustration of Belemnotheutis as drawn by Joseph Pearce. ==History and controversy==

.Right: a restoration by Joseph Pearce, the original discoverer of Belemnotheutis. It is also the illustration copied in 2008 using ~150 million year old ink recovered from the fossilized ink sac of Belemnotheutis antiquus. further inducing Pearce to protest what he viewed as erroneous descriptions of the specimens. In 1847, the London Geological Journal published a paper by Pearce of his objections to Owen's paper. At the same time the editor of the paper and another paleontologist, Edward Charlesworth, published an editorial criticizing Owen for deliberately failing to credit Pearce with the discovery of Belemnotheutis, as well as his apparent disregard to the opinions of less well-known paleontologists like Pearce. This was also the first time that Pearce described the specific epithet antiquus to the fossils. Pearce died later in the same year in May 1847 taking no further part in what was to become a controversy. Shortly after his death, the same paper published the support of William Cunnington, a fossil collector, for this description as opposed to Owen's conclusions. gaining supporters in other eminent paleontologists like Edward Forbes and Charles Lyell against Owen with regards to the true morphology of Belemnotheutis. By then the hostility between Owen and Mantell had escalated, Owen going so far as to oppose the awarding of the Royal Medal to Mantell However, he never recanted his earlier criticism of both Pearce and Mantell. ==References==