 |
Unit 80: Neoselachii |
|
The Vertebrates |
100: Neoselachii |
Abbreviated CladogramCHONDRICHTHYES | Neoselachii |--Galeomorphii | |--Heterodontiformes | `--+--Orectolobiformes | `--+--Carcharhiniformes | `--Lamniformes `--Squalea |--Squalomorpha `--Hypnosqualea |--Rajiformes `--Myliobatoidei |
Contents80.000: Overview |
Neoselachii:
last common ancestor of living sharks & all descendants.
Range: From the Triassic. Common from the Jurassic.
Phylogeny: Euselachii : Hybodontiformes + * : Squalea + Galeomorphii.
Characters: Large rostra common, with mouth opening ventrally; teeth with 1 or more layers of randomly oriented enameloid; $ teeth with "aprons" (= cingula?); $ m. adductor mandibularis present; very large brain; nasal capsules enlarged; hyomandibula articulates with jaw joint, and anterior end attached only by flexible ligaments (hyostylic); basibranchial elements directed posteriorly; paired occipital condyle; vertebral centra strongly calcified; notochord constricted; puboischiadic bar fused; non-lunate caudal fin; $ coracoids at least partially fused; pectoral fins with short metapterygial axis; 2 dorsal fins with spines; few mixopterygial (male "claspers") segments; placoid scales – single cusp with single pulp cavity (reduces turbulence); $ trunk lateral line canal closed (contra, Shirai (1996)); liver oil as primary buoyancy device.
Image: from Chondrichthyes.
Links: Maryland Geological Survey: Miocene Sharks Teeth of Calvert County; elasmo.com (big site!); Biology 356 (synapomorphies discussed); Shark Classification; Fossil Record of the Chondrichthyes; Neoselachii after Shirai, 1996 (cladogram); Devonian Times: About Sharks and Their Relatives (background); Topics in Shark Biology; Hors-série Requins 2 (French); A Listing of Fossil Sharks and Rays of the World; The EMR Spectra of Fossil Shark Teeth; Lecture Notes, Nat. Hist. Vert., Emporia State Univ..
References: deCarvalho (1996); Nelson (1994); Shirai (1996). ATW031108.
Range: From the Early Jurassic.
Phylogeny: Neoselachi : Squalea + * : Heterodontiformes + (Orectolobiformes + (Carcharhiniformes + Lamniformes)).
Characters: $ nasoral groove present; $ ethmoidal region curved downward; $ hyomandibular fossa in otic region, immediately behind orbit, with short otic capsule; spiracle small or absent; $ pharyngobranchials (ventral gill elements) expanded radially on ventral midline to form "pharyngobranchial blade"; $ vertebral centra extensively calcified; $ coracoids fully fused to form transverse bar; fin spines absent; $ trunk lateral line canal closed (contra, deCarvalho (1996)).
Links: Shark Senses - Enchanted Learning Software; Embryonic ELS - Sample Articles: Shark; Changes in Shark Classification; Galeomorphii; Hors-série Requins 2 (French); Galeomorphii (Mikko's Phylogeny); PII- S1055-7903(02)00333-0 (molecular phylogeny -- usual aberrant results).
References: deCarvalho (1996); Nelson (1994); Shirai (1996). ATW010730.
Heterodontiformes:
Heterodontus (Port Jackson shark).
Range: From the Early Jurassic.
Phylogeny: Galeomorphii : (Orectolobiformes + (Carcharhiniformes + Lamniformes)) + *.
Characters: 0.5 - 1.5 m. Mouth entirely anterior to orbits; labial cartilages in far anterior of mouth; tooth "aprons" (cingula?) present; nasoral grooves present; nasal capsules "trumpet-shaped" & well-separated from orbits; $ circumnarial skin folds present; $ rostral process of neurocranium absent; precerebral fossa present & rounded; supraorbital crest present; eyes without nictitating fold; m levator palatoquadrati also inserts on spiracle; spiracle small; superficial ophthalmic nerve exits brain with rest of Vth nerve; dorsal ends of branchial arches 4 & 5 attached, but not fused; 2 dorsal fins, with spines; dorsal & anal fin basals present; spiral intestinal valve (see Pelagic Shark Research Foundation); all oviparous; benthic feeder in shallow marine tropical & subtropical waters.
Links: NOVA Online | Island of the Sharks | Heterodontiformes; SHARK CLASSIFICATION- Enchanted Learning Software; Heterodontiformes: Bullhead Sharks; heterodontiformes; heterodontiformes; Heterodontiformes; Orden: (Spanish); Orders Summary; (Heterodontiformes) - MavicaNET (Russian & English); elasmo.com; Orden (Spanish); Oviparous Sharks.
References: deCarvalho (1996); Nelson (1994); Shirai (1996).
Image: Heterodontus francisci From ATLAS RYB (dead link).
Note: This taxon is considered to be quite distinct from other galeomorph sharks. ATW020801.
Orectolobiformes:
carpet sharks (e.g. Heteroscyllium), wobbegons (e.g. Orectolobus),
nurse sharks (e.g. Ginglymostoma), etc.
Range: From the middle Cretaceous.
Phylogeny: Galeomorphii :: (Carcharhiniformes + Lamniformes) + *.
Characters: Mouth very short and entirely anterior to orbits; labial cartilages in far anterior of mouth; tooth "aprons" (cingula?) present; prominent nasoral groove; $ nasal barbel enervated by superficial ophthalmic nerve; superficial adductor mandibulae absent; spiracle usually below orbit; $ m. levator palatoquadrati does not insert on spiracle (separate m. spiracularis); nasal capsules "trumpet-shaped" & well-separated from orbits; precerebral fossa absent; superficial ophthalmic nerve with separate foramen; small gill slits; 5th slit may overlap 4th posterior to origin of pectoral fin; dorsal ends of branchial arches 4 & 5 fused to form single plate ("gill pickaxe"); $ elongated & distally expanded pectoral meso- & metapterygium curving in opposite directions to create space between them (see Doornhaai - Skelet fig. 22 for nomenclature); 2 dorsal fins, without spines; dorsal & anal fin basals absent; cartilage at ventral margin of clasper elongated.
Links: NOVA Online | Island of the Sharks | Orectolobiformes (too slick); SHARK CLASSIFICATION- Enchanted Learning Software; Class Chondrichthyes; elasmo.com; Orectolobiformes (French -- a few pictures & some tables); Order Orectolobiformes (ADW, but this entry not too useful); Orectolobiformes (Mikko's phylogeny); orectolobiformes (species list); Haie - Faszinierende Tiere - Die Haiarten (T) (German -- very good site); Orden- (Spanish -- good, but basic); Whale Shark Research Group (large amount of basic biological information); ELASMO.COM Fossil -- Fossil Shark Genera (excellent; nurse shark paleontology); Description Whale Shark - Rhincodon typus (extensive, very high quality discussion of whale shark); Die ganze Welt der Haie - Orectolobiformes. (German: good, solid information); ORECTOLOBIFORMES (French: good, species-level diversity site); Carpet Sharks (a few useful words on ecology & mode of life); เกล็ดปลา ฉบับที่ 24 ตุลาคม 2544 (Thai? Possibly Bengali); Carpet sharks (Orectolobiformes) - MavicaNET (links: also in Russian); Ordre des Orectolobiformes (French: short, basic discussion); Orders Summary (FISHBASE).
References: deCarvalho (1996); Nelson (1994); Shirai (1996).
Image: Rhincodon (whale shark) ATW040101.
Carcharhiniformes:
(frequently spelled "Carchariniformes") ground sharks, cat sharks (e.g. Galeus), houndsharks (e.g. Triakis),
hammerheads (e.g. Sphyrna), etc.
Range: From the middle Cretaceous.
Phylogeny: Galeomorphii ::: Lamniformes + *.
Characters: mouth opens posterior to front of orbit; tripodal rostrum composed of lateral and 2 ventral rostral rods; precerebral fossa absent; nasal capsule close to orbit; ethmoid not curved downward; $ nictating lower eyelid (see Interactive way through the orders of sharks); superficial ophthalmic nerve with separate foramen; spiracle absent in some; tooth "aprons" (cingula?) absent; labially expanded bi-lobed tooth roots; nasoral groove absent; superficial adductor mandibulae absent; posterior 1-3 gill slits (of 5 total) located over pectoral fin; dorsal ends of branchial arches 4 & 5 fused to form single plate ("gill pickaxe"); gill rakers absent; 1-2 dorsal fins (one possible exception) without spines; anal fin present; dorsal & anal fin basals absent; cartilage at ventral margin of clasper elongated; intestinal valve spiral or scroll (?!); development may be oviparous, ovoviviparous, or viviparous; marine, estuarine & possibly FW habitats.
Links: elasmo.com; Carcharhiniformes: Ground or Whaler Sharks; Dierentuin.Net Dieren Database Grondhaaien (in Dutch); NOVA Online | Island of the Sharks | Carcharhiniformes; order Carchariniformes (ERMS taxonomic hierarchy); Orders Summary; SHARK CLASSIFICATION- Enchanted Learning Software; Order Carcharhiniformes; IWR: Taxa: Carcharhiniformes; CARCHARHINIFORMES; Carcharhiniformes; Carcharhiniformes; l3 - carcharhiniformes.jpg (Teeth); ORDRE DES CARCHARHINIFORMES; Classificazione genetico evolutiva - CARCHARHINIFORMES (Italian); Shores: Bonnethead; elasmo.com; carchariniformes (tooth pictures); CARCHARINIFORMES (very brief discussion); 133.htm (fossil).
Image: unidentified carcharhinid from Fishbase (former page).
References: deCarvalho (1996); Nelson (1994); Shirai (1996). ATW030322.
Lamniformes:
mackerel sharks (e.g. Lamna & Carcharodon), basking sharks (Cetorhinus),
etc.
Range: From the Late Jurassic
Phylogeny: Galeomorphii ::: Carcharhiniformes + *.
Characters: Large mouth, commonly extending well behind orbits; conical snout; nasoral groove absent; superficial adductor mandibulae absent; precerebral fossa absent; tripodal rostrum composed of lateral and 2 ventral rostral rods; nasal capsule close to orbit; ethmoid not curved downward; "lamnoid" dentition with enlarged anterior teeth, slightly to much smaller intermediate teeth, large lateral teeth, followed by much smaller posterior teeth; dental "aprons" (cingula?) absent; labially expanded bi-lobed tooth roots; eyes without eyelids; small spiracle commonly present posterior to orbits; superficial ophthalmic nerve with separate foramen; 5 gill slits; gill slits IV & V may be dorsal to pectoral fin; dorsal ends of branchial arches 4 & 5 fused to form single plate ("gill pickaxe"); $ secondary calcification of vertebrae; 2 dorsal fins without spines; dorsal & anal fin basals absent; cartilage at ventral margin of clasper elongated; $ intestinal ring (not spiral) valve; ovoviviparous, the fetuses of most forms augmenting their in utero nourishment by feeding on unfertilized eggs (oviphagy or oophagy).
Links: M24.htm; SHARK CLASSIFICATION- Enchanted Learning Software; elasmo.com; Order: Lamniformes; IWR: Taxa: Lamniformes; Lamniformes: Mackerel Sharks; NOVA Online | Island of the Sharks | Order Lamniformes; lamniformes; Classe5; Lamniformes; Mackerel Sharks - Order Lamniformes; Laminiformes; lam; Fossil Shark Genera; Orders Summary; M24.htm; Lamniformes; lamniformes; Jättehajar Lamniformes; Open Directory - Science- Biology- Flora and Fauna- Animalia- ...; lamniformes; Classificazione genetico evolutiva - LAMNIFORMES; Lamniformes; lam.
References: deCarvalho (1996); Nelson (1994); Shirai (1996).
Image: modified from deCarvalho (1996). ATW021022.
checked ATW050620
