INTEGBI 175LF Lecture Notes - Lecture 17: Acrodont, Rhynchocephalia, Agamidae
14 May 2018
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Lecture 17: LEPIDOSAURIA
●Synapomorphies:
○Streptostylic skull:
■Lost lower temporal arch of diapsid skull
■Removed strut that would usually fix quadrate ventrally
■Function: increased bite force by allowing pterygoideus muscle
○Pleurodont dentition:
■Teeth attached to labial side of jaw
■Continually shed thru life
■Adaptation for insectivory?
■Acrodont : in sphenodon, agamidae, chamaeleonidae - teeth fused to labial and
lingual surfaces of jaw and to adj teeth - no replacement
○Caudal autonomy:
■Breakage w/in a vertebrae
■Cartilaginous rod grows out
■Fracture plane : caudal muscle and fascia in bundles that facilitate separation
■Lost in many lineages, some alt means evolved
○Hooked 5th metatarsal : muscle inserting on this bone elevates foot onto 1st 4
metatarsals
○Synchronous skin shedding
●Integument :
○Fewer glands - concentrated at specific sites, none toxic
○Scales and osteoderms
○Sense organs : hair cells that are mechanoreceptors
●Rhynchocephalia - Tuataras:
○Sphenodontidae - Sphenodon punctatus/guntheri → sister taxon of Squamata (240 mya)
○Range: small islands of New Zealand, 1 mainland reintroduction
○Fossils: late Jurassic, Cretaceous, absent from Cenozoic except for NZ
■Extinct had diversity of body forms
■Some aquatic, less than 1m long, powerful tails, lat skulls
○Ecology:
■Nocturnal
■Burrows shared w/ fairy prions
■Insectivorous, but not strictly
■Territorial, M-biased dimorphism
○Description:
■Heterodonty : acrodont canines, incisor-like bony premax downgrowths
■Lower temporal arch fixed to quadrate → secondary loss of streptostyly
■Plesiomorphic (primitive) features:
●Absence of penis → cloacal apposition
●Separation of vomeronasal organ from oral cavity
●Gastralia : rib-like structures running btw sternum and pubis,
free-loating
Document Summary
Lost lower temporal ar(cid:283)h o(cid:321) diapsid skull. Remo(cid:475)ed st(cid:418)ut that (cid:476)ould usuall(cid:482) (cid:481) (cid:417)uad(cid:418)ate (cid:475)ent(cid:418)all(cid:482) Fun(cid:283)tion: in(cid:283)(cid:418)eased (cid:282)ite (cid:321)o(cid:418)(cid:283)e (cid:282)(cid:482) allo(cid:476)in(cid:322) pte(cid:418)(cid:482)(cid:322)oideus mus(cid:283)le. Teeth atta(cid:283)hed to la(cid:282)ial side o(cid:321) ja(cid:476) A(cid:283)rodont : in sphenodon, a(cid:322)amidae, (cid:283)hamaeleonidae - teeth (cid:321)used to la(cid:282)ial and lin(cid:322)ual su(cid:418)(cid:321)a(cid:283)es o(cid:321) ja(cid:476) and to adj teeth - no (cid:418)epla(cid:283)ement. Fra(cid:283)ture plane : (cid:283)audal mus(cid:283)le and (cid:321)as(cid:283)ia in (cid:282)undles that (cid:321)a(cid:283)ilitate sepa(cid:418)ation. Lost in man(cid:482) linea(cid:322)es, some alt means e(cid:475)ol(cid:475)ed. Hooked 5th metatarsal : mus(cid:283)le inse(cid:418)tin(cid:322) on this (cid:282)one ele(cid:475)ates (cid:321)oot onto (cid:1680)st (cid:1683) metata(cid:418)sals. Fe(cid:476)e(cid:418) (cid:322)lands - (cid:283)on(cid:283)ent(cid:418)ated at spe(cid:283)i (cid:283) sites, none to(cid:481)i(cid:283) Sense organs : hai(cid:418) (cid:283)ells that a(cid:418)e me(cid:283)hano(cid:418)e(cid:283)epto(cid:418)s. Sphenodontidae - sphenodon punctatus/guntheri siste(cid:418) ta(cid:481)on o(cid:321) s(cid:417)uamata (cid:1827)(cid:1681)(cid:1683)(cid:1679) m(cid:482)a(cid:1828) Ran(cid:322)e: small islands o(cid:498)(cid:321) ne(cid:476) zealand, (cid:1680) mainland (cid:418)eint(cid:418)odu(cid:283)tion. Fossils: late ju(cid:418)assi(cid:283), c(cid:418)eta(cid:283)eous, a(cid:282)sent (cid:321)(cid:418)om cenozoi(cid:283) e(cid:481)(cid:283)ept (cid:321)o(cid:418) nz. Some a(cid:417)uati(cid:283), less than (cid:1680)m lon(cid:322), po(cid:476)e(cid:418)(cid:321)ul tails, (cid:500)lat skulls. Heterodonty : a(cid:283)(cid:418)odont (cid:283)anines, in(cid:283)iso(cid:418)-like (cid:282)on(cid:482) p(cid:418)ema(cid:481) do(cid:476)n(cid:322)(cid:418)o(cid:476)ths.
