Sarcopterygian Fishes Flashcards
What are the three shared diagnostic features of sarcopterygian fishes?
Intracranial joint: between anterior and posterior parts of the brain, use muscles that are homologous to human eye muscles to to power the joint
Cosmoid scales in basal members: thick enamel and thin dentine over 2 layers of bone
Lobe fin: muscles are positioned along skeletal elements of fins, supported by bones called mesomeres, single bone connected to pectoral girdle, radial bones and fin rays are symmetrical in Actinistia and Dipnoid
What are the two most basal sarcopterygian fishes?
Actinistia and Dipnoid (coelacanths and lungfishes)
What are the shared diagnostic features of Actinistia? How many extant species are there and where do they live?
There are two extant species in the genera Latimeria, and they live in the Indian ocean.
Rostral organ for electroreception: 3 pair of tubular canals which are placed similarly to the Ampullae of Lorenzini
Diphycercal caudal fin: one undifferentiated lobe, vertically symmetrical across the vertebral column
Vestigial lung filled with fatty tissues for buoyancy
High concentration of urea in the blood
What are the shared diagnostic features of Dipnoi? What kind of water do they live in and what feeding do they use?
They live in freshwater and rely on suction feeding
Loss of premaxilla, maxilla, and dentary, jaw supported by one bone in upper and lower jaw
Holostylic jaw suspension (upper bone fused with cranium)
Reduced fin but still supported by mesomeres
Respirations using both gills and lungs, lungs have small sacs similar to alveoli
Well developed sensory system for land and water living (Ampullae of Lorenzini, lateral line system, enlarged olfactory bulb, many taste buds as well as vomeronasal organ
Characteristics of Australian Lungfish
Large genomic size (one of the largest of animals, mostly noncoding regions), large cells, complex courtship and territorial behaviour (men circle around women, and compete with other males for who can breathe air the best)
Characteristics of African Lungfish
reduced whiplike/thread tail, cosmoine scales reduced, some parental care (make bowl nest and males protect the nest), they can burrow and estivate where they fold themselves into a U shape and then secrete mucus which hardens around them like a cocoon that has antibacterial properties
What are the four clades of fossil sarcopterygian fishes?
Onchyodontia, Porolepiformes, Osteolepiformes, Elpistostegalia
What are some characteristics of Onchyodontia? What is their diagnostic features?
They are the most basal fossils, they may be the sister group to Actinistia, and their diagnostic feature is the tooth whorl with mobile tusk-like teeth, they are ambush predators
What are some diagnostic features of Porolepiformes?
Predators, their diagnostic features include tapering fins, heterocercal caudal fin, jaw with individual tooth (unlike the tooth plated in Dipnoi) and they resemble Devonian lung fish with fins/tails
What are the diagnostic features of Osteolepiformes? What are the two clades contained within it?
This is a polyphyletic clade containing some stem tetrapod, their diagnostic features include 2 dorsal fins and one anal fin, as well as skull with an intracranial joint
This clade contains rhizodontidae and tristichoperidae
What are characteristics of Rhizodontidae?
They are freshwater predators, 7m long, their diagnostic features are poorly know as their fossil record is very fragmented
What are some characteristics of Tristichoperidae?
The most well studied specimen is Eusthenopteran, their DF include a trifurcate caudal fin (different from diphycercal because it does not have the centra lobe) and they also have labyrinthodont teeth which contain folds of enamel and dentine therefore when they are cross-sectioned they appear like a maze
What are characteristics of Elpistostegalia? What clades are contained within this one?
This is a paraphyletic clade that is closer to tetrapod than Osteolepiformes and their diagnostic features include a flattened skull with dorsally placed eye as well as no dorsal or anal fins. The two clades contained within this one are Panderichthys and Tiktaalik.
What are features of Panderichthys?
They are ambush predators, and they live in shallow water, their DF include elongated rostrum, and a modified humerus to prop their head above the water
What are features of Tiktaalik?
They retain the spiracle and have no bony connection between skull and pectoral girdle, their forelimb has many synovial joints, and they may have cranial kinesis that makes them capable of suction feeding.
