Quiz
Evolution of Marine Reptiles
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1Amphibia-Amniota: Basic anatomical and reproductive differences
Reptiles
Skin covered by scales.
Eggs are laid in ground, developing embryonary membranes and [blank_start]apergaminate[blank_end] (soft) or calcareous (hard) shells. Some groups can develop embryo retention and [blank_start]viviparity[blank_end].
Larval stages [blank_start]do not exist[blank_end].- Aapergaminate
- Bviviparity
- Cdo not exist
2Key terms
Reptiles: all members of the amniote clade
that includes living turtles, lizards, crocs
[blank_start]Diapsids[blank_end]: reptiles with two skull openings
behind orbit: the lizard-croc clade
Neodiapsid: diapsid clade that includes
[blank_start]Younginiformes[blank_end] + Sauria
Lepidosaurs: tuatara and kin
(rhynchocephalians) and squamates
[blank_start]Squamates[blank_end]: snakes, lizards, amphisbaenians
( = ‘worm-lizards’)
Archosauromorphs: archosaurs and close
relatives (like protosaurs & [blank_start]rhynchosaurs[blank_end])
Archosaurs: [blank_start]crocodiles[blank_end] and kin, pterosaurs,
dinosaurs and kin (including birds)- ADiapsids
- BSquamates
- Ccrocodiles
- DYounginiformes
- Erhynchosaurs
3Earliest reptiles have an [blank_start]anapsid[blank_end] skull
(= where there are no post-orbital openings)
The diapsid skull evolved from
an anapsid ancestor…
The diapsid skull (or a modified version
of it) is present in lizards, snakes, crocs, birds- Aanapsid
4Turtles have an anapsid skull and hence have
conventionally been placed outside of [blank_start]Diapsida[blank_end].
However, molecular data places them deep
within Diapsida. If correct, this means that they
evolved their [blank_start]anapsid condition from a diapsidone[blank_end].- Aanapsid condition from a diapsidone
- BDiapsida
5Archosauromorphs: archosaurs and their close relatives
Non-archosaurian archosauromorphs include [blank_start]protorosaurs[blank_end], trilophosaurs and rhynchosaurs. Mostly terrestrial [blank_start]Triassic[blank_end] animals; include small, lizard-like predators and omnivores, long-necked amphibious forms, specialised herbivores.- Aprotorosaurs
- BTriassic
6[blank_start]Lepidosaurs[blank_end]: lizards, snakes, tuatara and their relatives
Mostly small diapsids with flexible skulls: key events in evolution include appearance of different [blank_start]kinetic zones[blank_end] in skull. Post-Triassic group, many key divergences in [blank_start]Jurassic and Cretaceous.[blank_end]- ALepidosaurs
- Bkinetic zones
- CJurassic and Cretaceous.
7[blank_start]Tuatara[blank_end] (Sphenodon): two species of chunky, lizard-like diapsids, endemic to New Zealand. Endangered, now restricted to offshore
Islands.
Enlarged [blank_start]premaxillary[blank_end] teeth and marginal teeth all [blank_start]fusedto jaw edges[blank_end]. Propaliny
present; halves of lower jaw
rotate about symphysis.
[blank_start]Shearing or sawing[blank_end] motion
used to break up prey.
Complete LTB long thought to be a ‘primitive’ feature;
contributed to the idea that Sphenodon is an archaic relict.- AShearing or sawing
- Bfusedto jaw edges
- CTuatara
- Dpremaxillary
8Squamates: over [blank_start]7500[blank_end] species
‘lizards’ [blank_start]paraphyletic[blank_end] to amphisbaenians
and snakes.- A7500
- Bparaphyletic
9Reptile physiology and anatomy makes the transition to marine life relatively easy. However, to take to marine life a reptile still has to…
--- move efficiently in the water
--- feed effectively in the water
--- [blank_start]regulate salt concentrations[blank_end]
….. oh, and cope with [blank_start]buoyancy[blank_end], reproduction and heat loss too…- Aregulate salt concentrations
- Bbuoyancy
10The evolution of locomotion in water, examples from the marine reptile fossil record
[blank_start]Discontinuous locomotion[blank_end]: Where propulsion is only generated during the [blank_start]power stroke[blank_end],
e.g., paddling, rowing (bears, paddling seabirds, swimming rodents, diving ducks)- ADiscontinuous locomotion
- Bpower stroke
11Continuous locomotion: there’s [blank_start]axial locomotion[blank_end], powered by body and/or tail. Axial locomotors practising continuous locomotion can be axial [blank_start]undulatory[blank_end] swimmers (using wave-like sweeps of tail) or axial [blank_start]oscillatory[blank_end] swimmers (using swivelling of propulsive structure, like tail fin). Another category within continuous locomotion: [blank_start]paraxial locomotion[blank_end] (using lift- or drag-based limbs).
- Aaxial locomotion
- Bundulatory
- Coscillatory
- Dparaxial locomotion
12Trend seen frequently in evolutionary history of marine reptiles. Transition from axial [blank_start]undulatory[blank_end] swimmers to axial [blank_start]oscillatory[blank_end] swimmers. Seen in ichthyosaurs, [blank_start]crocodyliforms[blank_end], mosasaurs.
- Acrocodyliforms
- Bundulatory
- Coscillatory
13Trend seen rarely in evolutionary history of marine reptiles. Transition from axial undulatory swimmers to paraxial swimmers. Seen in [blank_start]sauropterygians[blank_end].
- Asauropterygians
14Salt and sea-water
Seawater contains about 35g of salt per liter. Marine mammals void unwanted salt via [blank_start]efficient kidneys[blank_end] that produce concentrated [blank_start]urine[blank_end]. Reptiles don’t have such efficient kidneys: instead they use salt-excreting skull glands.
Marine iguana salt glands
are in the [blank_start]nasal cavity[blank_end]
Crocodile salt glands
are on the tongue
Sea snake salt glands
are [blank_start]under the tongue[blank_end]
Sea turtle salt glands
are between the eyes
Seabird salt glands are set in bony
depressions above the eyes- Aefficient kidneys
- Burine
- Cnasal cavity
- Dunder the tongue
15Sauropterygians
Major clade of Mesozoic marine reptiles, initially mostly [blank_start]Tethyan[blank_end] but worldwide by Jurassic.
[blank_start]Placodonts[blank_end], pachypleurosaurs, [blank_start]nothosaurs[blank_end], pistosaurs and plesiosaurs.
Key characters: [blank_start]euryapsid[blank_end] condition, retracted external nostrils, closed palate extending to braincase, absence of
several skull bones (lacrimal, tabular, postparietal, supratemporal), large retroarticular process, scapula superficial to
clavicle, small ilium etc.- ATethyan
- Bnothosaurs
- Ceuryapsid
- DPlacodonts
16Placodonts
Triassic sauropterygians from Europe, Middle East and China, famous for their [blank_start]crushing[blank_end]
dentition. Evolved an elaborate, turtle-like armour composed of interlocking [blank_start]scutes[blank_end].- Acrushing
- Bscutes
17[blank_start]Pachypleurosaurs[blank_end]
Small amphibious Triassic sauropterygians (to 2m) known
from 100s of specimens. Some suction-feeding features.
Embryos show that [blank_start]viviparity[blank_end] present already.- APachypleurosaurs
- Bviviparity
18Viviparity evolved early on within Sauropterygia – before these animals evolved [blank_start]giant size[blank_end] and pelagic habit
- Agiant size
19Nothosauroids
The best known nothosauroid: Nothosaurus from Middle and Upper Triassic Europe, Middle East and China. Several species ranging from 1.25 to 3.5 m long. Fantastic [blank_start]teeth[blank_end]!- Ateeth
20Pistosaurs: ancestors of plesiosaurs
Several Late Triassic taxa appear to be ‘[blank_start]proto-plesiosaurs[blank_end]’. Resemble plesiosaurs in having
[blank_start]retracted external[blank_end] nostrils, parietal crest, a simplified humerus shape and other characters.
Enlarged, wing-shaped hands suggest [blank_start]paraxial Locomotion[blank_end] (presumably underwater ‘flight’).- Aproto-plesiosaurs
- Bparaxial Locomotion
- Cretracted external
21Examples of non-plesiosaurian sauropterygians
[blank_start]nothosaur[blank_end]
[blank_start]pistosaur[blank_end]- Anothosaur
- Bpistosaur
22Plesiosaurs
Carnivorous Mesozoic marine reptiles
Approx. [blank_start]200-65 million[blank_end] years ago
Plesiosaurs are derived sauropterygians
Sauropterygia – including placodonts, pachypleurosaurs, nothosaurs, pistosaurs- A200-65 million
23Quick history of plesiosaurs
Plesiosaurs evolved during the
Late [blank_start]Triassic[blank_end] from [blank_start]pistosaurs[blank_end].
Several lineages evolved giant
size (10m+, 5tons+) during
Jurassic & Cretaceous.
‘Pliosauromorphs’ ([blank_start]big[blank_end] heads,
[blank_start]short[blank_end] necks) evolved several
times from ‘plesiosauromorphs’
([blank_start]small[blank_end] heads, [blank_start]long[blank_end] necks). Most
‘pliosauromorphs’ belong within
Pliosauroidea.
Plesiosauroids include very long-
necked elasmosaurids as well
as long-snouted polycotylids.
Plesiosaurs mostly pelagic ocean-
going animals, but there were
[blank_start]estuarine and freshwater[blank_end] lineages
within Leptocleidia.
Mass extinction end of Cretaceous.- Abig
- Bshort
- Csmall
- Dlong
- Eestuarine and freshwater
- FTriassic
- Gpistosaurs
24The skull and dentition
Modified diapsid (‘euryapsid’) condition: [blank_start]loss of lower temporal fenestrae[blank_end]
Position of the intenal and external nares
Single large temporal fenestra- Aloss of lower temporal fenestrae
25Polycotylid debate
Traditional Classifications treat them as [blank_start]Pliosaurs[blank_end]
But apart from the [blank_start]large head[blank_end], most of the characters are typically plesiosauroid.
So, [blank_start]neck length and size of head[blank_end] are unreliable
It now makes more sense to refer to plesiosaurs as either pliosauromorph or plesiosauromorph.- APliosaurs
- Bneck length and size of head
- Clarge head
26Mesozoic plesiosaur ‘pregnant female’ with a [blank_start]foetus inside the body cavity[blank_end]
- Afoetus inside the body cavity
27Ichthyosaurs
Carnivorous Mesozoic marine reptiles
Approx. [blank_start]200-90 million[blank_end] years ago (before [blank_start]K-T extinction[blank_end])
Exact origin of ichthyosaurs unknown
Teeth set in [blank_start]groove[blank_end] (not sockets)
Ichthyopterygia – increasingly [blank_start]fish-like[blank_end] through time
Huge [blank_start]eyes[blank_end]- A200-90 million
- BK-T extinction
- Cgroove
- Dfish-like
- Eeyes
28The big question about all the Mesozoic marine reptile lineages we’ve looked at
(thalattosaurs, hupehsuchians, sauropterygians, also ichthyosaurs) is: where do their affinities lie within Reptilia?
Difficult to resolve because all have a strongly modified morphology: in the skull, diapsid condition has been modified
to [blank_start]euryapsid condition[blank_end] (where there’s a supratemporal fenestra, but no obvious
laterotemporal fenestra).
Seems that all of these lineages are within
[blank_start]Neodiapsida[blank_end]. Sauropterygians have
sometimes been argued to be close to
lepidosaurs; other studies suggest that all
of these lineages are archosauromorphs.- Aeuryapsid condition
- BNeodiapsida
29Cretaceous lizards invade the seas
During the ‘mid’ Cretaceous (from c [blank_start]100Ma[blank_end]), several lineages of anguimorph lizards (related to [blank_start]monitorsand gila monsters[blank_end]) took to the seas as mid-sized (c1m), long-bodied, shallow-water foragers on reefs etc.
From shallow marine sediments of Europe, Middle East, N America. Dolichosaurs and aigialosaurs.
[blank_start]Viviparity[blank_end] was present,
even in these mid-sized
amphibious lineages.
Carsosaurus with 4
embryos in body cavity.- A100Ma
- BViviparity
- Cmonitorsand gila monsters
30Mosasaurs
Large to gigantic aquatic anguimorphs (mostly marine).
Flexible zone in [blank_start]lower jaw[blank_end], evidence for [blank_start]ratchet[blank_end] feeding. Evolutionary trends: longer snout, retracted
Nostrils, longer and wider paddle-like limbs, more
paddle-like tail, with some evolving [blank_start]heterocercal[blank_end] tail.- Alower jaw
- Bratchet
- Cheterocercal
Informações
- Descrição
- Evolution of Marine Reptiles, Neil lecture
- Autor
- Ethan Ross
- Idioma
- English
- Visualizações
- 78
- Etiquetas
- Avaliação
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