Bullhead Sharks (Order Heterodontiformes)
Order: [Group] Heterodonti Garman, 1885, Bull. Mus. Comp. Zool. Harvard, 12(1): 30, emended to Order Heterodontiformes.
Number of Recognized Families: 1.
Diagnostic Features Of Bullhead Sharks
Bullhead Sharks are the only living sharks with two spiny dorsal fins and an anal fin, a pig-like snout, a small front mouth with enlarged molar-shaped teeth on the back of the mouth, supraorbital combs of rough skin and a pair of paddle-like fins enlarged in the first gliding slot. The muzzle is short and pressed, with rounded posterior teeth and rusty barbel. The diagnostic feature is that the head has an elevated comb and the eyes are not pressed but widened. The eyes are dorsolateral to the head, nictified, the lower eyelid secondary to the subocular pouch and the upper eyelid not fused with the eyeball.
The mouth is small and terminal on the head, arched, with a short end in front of the back corner of the eye. Nostrils are diagonal to the front of the muzzle; barbel is a prominent circumferential groove that occurs with the opening of the nostrils; deep nasal grooves connect the exstroopening with the mouth; anterior nostril flap reaches the mouth. There are five pairs of Gili openings on either side of the head, two or three on the pectoral fin. Labial furrows are large and present on both jaws. Spiracles are small and face the eye at eye level.
The teeth that distinguish the jaw are small anterolateral teeth, enlarged molars, posterior gaps, small interstitial teeth, anterior and lateral teeth of the maxilla, anterolateral teeth are orthodontic in histological structure and posterior teeth are osteodontic.
Dermal denticles covering the whole body, but no enlarged spines or spines. Logs cylindrical, but not flattened or radial. Caudal stems with lateral dermal burrs and quills.
Pectoral fins and skeleton Tribasal and dibasal propterygia fused into mesopterygia In some species, the property is in contact with the metapterygian radii on the proximal segment of the pectoral fin, and semiplesodic radii extend from the basal fins (radial number 15-19, with 2-8 segments). Chest belt scapulocoracoids tall, U-shaped, with medial joints and superscapulae in direct but not in contact with the spine. The pelvic fins are small, with continuous ventilation openings along their inner rim. They are large but do not expand into rays and have triangular anterior lobes that cover the gilding opening.
At the origin there are two dorsal fins, the first at the front of the pelvic fin at the base of the pectoral fin; the dorsal fin skeleton is a segmented radiai with enlarged interstitial cartilage, with a single basal plate carrying a large fin spine. The tail fin has a long back flap and a short abdominal flap, above which the vertebral axis is raised in heterocerca. The staple is a short siphon between the abdomen and pelvic fin, the basis for the staple sacs, its glans a large pseudosiphon that covers the rhipidium and its spines, and the dorsal and ventral marginal staple skeletons are developed from the dorsal marginal roll tube and staple canal.
The total number of vertebrae is 103-123, that of precautionary vertebrae 60-81. Severe secondary calcification in the form of several radii extending from basai, intermediate wedges, annuli and diagonal calcification.
Postrum, nasal capsule, trumpet-shaped subnasal fenestrae, base communication channel, antorbital cartilage, orbit, incomplete preorbital wall, strong supraorbital ridge, strong suborbital shelf, separate foramina, hyomandibular nerve, separate foramina and superficial ophthalmic nerve, incomplete postorbital walls, lateral commissions, lateral head veins, oc Jaw: elongated maxilla, palate squares, low crest-like orbital process, articulated nasal capsule and orbit, horizontal grooves, contact with the ethmoid region, basal plate, suborbinal shelf, orbital process does not penetrate the supraorbital ridge. The head muscles include enlarged vertical preorbital, transverse fibers, narrow palatal levator, separate first dorsal constrictors, poststorbinal process that does not extend into orbit, adductors, mandibular muscles, not segmented, not notched, mouth gaping, discrete cranial andibular muscles, mandible, orbital wall, tonsibulocutaneous muscles, maxillary skin, postocular and eyelid muscles. Broad, elongated basihyoid, posterior two pharyngobranchial, last epibranchial, fused, yoke-shaped elements.
Eggs are laid in unique helical eggs. Intestinal valves of the conicospiral type have seven turns.
Distribution, habitat, biology, interests, fisheries, human impacts and local names (see family Heterodontidae). Hetodontiformes are a small, characteristic group of sharks that are recognized at the highest level as an independent taxa (genus or family). They have a long fossil history dating back to the Mesozoic period and are generally considered to be hybodont sharks, along with other extinct Euselachians, which have powerful dorsal fins, spines and anal fins.
Bullhead sharks were discovered in Australia in the late 18th century in the form of Port Jackson (Squalusportusjacksonimeyer) (1793), of which there are several synonyms. After two genus groups – Heterodontus (Blainville, 1816) and its junior synonym Cestracion (Oken, 1817 ) – it was classified as a linear shark (genus Squalus ) and proposed as a subgenus of the genus Squalus, but most later authors recognized it as a genus.
Bonaparte (1838) proposed a new subfamily, Cestraciontini, within the family Squalidae ; Muller and Henle (1839) proposed the new family Cestraconte (Cestracions); Gray (1851) proposed an entirely new tribe of Hetodontus, from which Hetodontus was elevated to the rank of a family, Hetidontoidae; Gili (1862b). Swainson (1849) placed Cestacion together with various squaloids and other sharks in the family of the Squalidae (Centrininae). Van der Hoeven (1858) placed them together with other sharks in the family Selachii, and Hasse (1879) classified the species in his group 3, acrodontes, as a familial classification. Many writers of the nineteenth and early twentieth centuries that used the genus Cestratius to favor HetaDontus also recognized families of Cest Racionidae variants, including Muller (1845) (family Cest racionidae variant) and Bleeker (1859) and families Cestricionoidei and Dumeril (1865) as well as families of Owen (1866), Gunther (1870), Woodward (1889, 1898), Zittel and al.
The use of heterodontus as the oldest synonym for Cestracion began in the second half of the 19th century and prevailed throughout most of the 20th century. Hetodontidae family was founded by Gili (1872, 1893), Jordan and Gilbert (1883), Jordan & Evermann (1896), Bridge (1910), Jordan (1923), White (1936, 1937), Bertin (1939a), Whitley (19 1940), Fowler (1941, 1966), Romer (1945, 1966) The concept of a separate ordinal group within the family HETODontidae goes back to Garman (1885), who grouped all heterodontii under Gili and in 1893 included the family into the separate order Proarthri, with the subordination Proarthris under Jordan and Evermann. The group was grouped with various fossil sharks, referred to by early authors as hybodons, and with different families of living sharks, including lamnoids, carcharhinoids, and squaloids.
White (1936-1937) recognized the Heterodontea order, which was listed by Bertin (1939a) as the subordination of the Hetodontiformes and Berg (1940) as subordination of the same order, while Bigelow and Schroeder (1948) had the Hetosontidea subordination. Goodrich (1909) included the Hetidontidae in the subordination Hetomonti, and Garman (1913) included them in the group Centracoidei. Most later writers tended to give the Hetoderidae family its own order, Hetudontiforme, including the authors of the Compagno (1973, 1977, 1984, 1988, 1999) and this work. The anatomy of heterodontoids has been described by Gegenbaur (1865-1872), Haswell (1885), Daniel (1914-1915) and 1928, Holmgren (1941), Kesteven (1942), Compag novices (1973), Shirai (1992, 1996) and de Carvalho (1996), and the general morphology is systematic and summarized by Dumeril (18 1865), Miklouho, Maclay and Macleay (1879-1886), Gunther (1870), Regan (1908b), Garman (1913), Smith (1922), Taylor (1972) and CompagNO (1973). It is probable that they are related to lamnoids, carcharhinoids and orectoloboids, and the most probable hypothesis is that they could be sister groups of the latter (see Discussion by Compag NOvices, Compagnos 1973, 1977 and 1988, Shirai 1996 and de carvalho 1996).