Squamata
The Vertebrates Pythonomorpha: Macrostomata

Squamata: Pythonomorpha: Macrostomata

Abbreviated Dendrogram
Squamata ├─Iguania └─Scleroglossa │ └─Pythonomorpha ├─Mosasauroidea └─Serpentes ├─Scolecophidia └─Alethinophidia ├─Aniloidea └─Macrostomata ├─Madtsoiidae └─┬─Pachyophiidae └─┬─Boidae └─Caenophidia ├─Acrochordoidea └─Colubroidea ├─Colubridae └─Viperidae
Contents

Overview
Squamata
Iguania
Acrodonta
Scincogekkonomorpha
Scleroglossa
Scincomorpha
Anguimorpha
Pythonomorpha
Mosasauridae
Scolecophidia
Alethinophidia
Macrostomata
Colubroidea
Dendrogram
References


 Taxa on This Page

  1. Acrochordoidea
  2. Boidae
  3. Caenophidia
  4. Macrostomata
  5. Madtsoiidae X
  6. Pachyophiidae X

Descriptions 


Macrostomata: Crotalus > Anilius. snakes with large gapes (boas, cobras, vipers)

Range: fr upK worldwide.

Alethinophidia:: Aniloidea + *: Madtsoiidae + (Pachyophiidae + (Boidae + Caenophidia))

Characters: $ enlorged posterodorsal toothed process of dentary [Z98]; toothed anterior process of pterygoid [Z98]; $ basipterygoid processes reduced, with articulating surface facing ventrally [Z98]; $ free-ending process of supratemporal [Z98]; $ dorsal surface of prootic concealed by supratemporal [Z98]; quadrate vertical or posteriorly directed [Z98]; $ quadrate suprastapedial process absent (except Xenopeltis) [Z98];

References: Zaher (1998) [Z98]


Madtsoiidae: Alamitophis, Gigantophis (~9m! see image at fossili), Wonambi. Some very large. Mostly known from isolated vertebrae.

Range: mK-lwPle of Gondwana (SAm, Aus. & Egypt). Latest South American finds are of Ec age.

Phylogeny: Macrostomata: (Pachyophiidae + (Boidae + Caenophidia)) + *.

Characters: generally cylindrical body[C&A]; skull long & low [S&L]; upper jaw tightly fixed to skull [S&L]; palate very broad [S&L]; palatine in extensive contact with vomer [S&L]; small facets on pterygoids for basipterygoid articulation; snout rounded [S&L]; ligamentous maxilla - premaxilla connection [S&L]; prefrontal sutured to maxilla, but movable on frontal [S&L]; frontal - nasal articulation sutured and rigid [S&L]; jugal probably retained [S&L]; supratemporal and/or quadrate projected posteriorly [S&L]; braincase narrow betwen orbits, widening posteriorly [S&L]; paracotylar foramina present; $ "parazygantral foramina" (i.e. foramina on the vertebrae lateral to the zygantra) [A]; prezygapophyseal processes absent; synapophyses (?!) located low from centrum [A][S&L]; tall, narrow vertebrae with single hypapophyses on anterior trunk [S&L]; vertebrae elongate and become lower more posteriorly [S&L]; trunk ribs curved throughout, with proximal facets slightly constricted between diapophyseal & parapophyseal processes; no limb or girdle elements [S&L].

Links: Faiyum introduction; fossili Italian); Faiyum 2nd; News in Science 27/01/00 First snakes may have come from the water (Wonambi); A twist in the tail of snake evolution (Best on the Web); un485.pdf third page); ABC Online Forum (comment from "eric").

References: Albino 2000) [A]; Caldwell & Albino 2001) [C&A]; Scanlon & Lee (2000) [S&L]

Note: Apparantly, the only decently known madtsoiid is Wonambi. Thus the characters above are almost all apomorphies of Wonambi.


Haasiophis hind limbPachyophiidae:   Haasiophis, Pachyophis, Pachyrachis, Podophis.

mK-upK of the Middle East & E.Eur.

Macrostomata:: (Boidae + Caenophidia) + *.

Characters: up to 1.1 cm, with laterally compressed bodies [C&A]; probably wide gape [C&A]; pterygoids with teeth [T]; toothbearing process of dentary long [T]; long, recurved pterygoid teeth [C&L]; mandible not fused; $ intramandibular joint anterior (Pachyrachis) [C&L]; angular not exposed on medial surface of jaw [C&L]; $ large rectangular coronoid process (Pachyrachis) [C&L]; palatines do not contact ectopterygoid [T]; transverse process of pterygoid gently curved and receives ectopterygoid on lateral surface [T]; lateral edge of ectopterygoid not straight [T]; anterior end of ectopterygoid invades surface of maxilla, approaching posteroventral corner of orbit [T]; reduced basipterygoid processes [C&L]; lacrimal absent [C&L]; ventral tip of postorbital contacts (or almost contacts) ectopterygoid, completing orbital margin [T]; postorbital & postfrontal fused (Pachyrachis & maybe Haasiophis) [C&L]; supratemporal process of parietal not well developed [T]; "free ending" (?) process of supratemporal present [T]; braincase completely encased; prootic fully concealed by supratemporal or parietal in dorsal view [T]; quadrate vertical (cephalic condyle & mandibular condyle at same anteroposterior level) [T]; no or vestigial stapedial process of quadrate cephalic condyle [T]; $ quadrate anteroposteriorly expanded (Pachyrachis) [C&L]; ~140 trunk vertebrae; pachyostotic mid-dorsal vertebrae & ribs [C&L] [C&A]; well-developed hindlimb, with pelvis outside ribs; may have sacrum [C&L]; femur, tibia, fibula and some tarsals present; astragalus & calcaneum not fused [C&L]; inhabited sheltered marine reef environments [C&A].  

Links: ScienceDaily Magazine: New Fossil Snake With Legs; Argument About Snake Evolution Rekindled by Fossil; SNAKES.SMU.

Reference:Caldwell & Albino (2001) [C&A]; Caldwell & Lee (1997) [C&L]; Lee et al. 1999); Tchernov et al. 2000) [T]; Zaher (1998).

Note: [1] The characters above from [T] include only derived features, shared by both known genera. [T] also identify 3 synapomorphies of this group: $ outer orbital (lateral) margin of prefrontal slanting anteroventrally; $ ascending process of maxilla well-developed; $ coronoid process from coronoid bone only. All 3 are supposed reversals, and one might guess that the first two are correlated. This is indeed a weakly supported group. However, the derived characters do include strongly consistent (CI=1) macrostomate synapomorphies, so the paper's central conclusion -- that the 'Ein Yabrud specimens are macrostomates -- is well supported. [2] There now appears to have been a thriving and diverse community of Cretaceous marine snakes on both the Northern and Southern margins of the Tethys Sea in Late Cretaceous times. [C&A]. C&A note that the Southern population necessarilly places this group close in time and space to the Gondwanan madtsoiids. 010901.


Boidae: boas & pythons.

fr upK.

Phylogeny:Macrostomata::: Caenophidia + *.

Squamosal and quadrate lengthened. Few diagnostic features: intermediates between Scolecophidia and advanced snakes.

Links: The Boa Constrictor Subspecies.


Caenophidia:   = Xenophidia = Colubroidea) "advanced," poisonous snakes and relatives

Range: fr Ec?; cosmopolitan

Phylogeny:Macrostomata::: Boidae + *: Acrochordoidea + Colubroidea.

complete absence of pelvic girdle.

Links: Snakes; Caenophidia after Gravlund, 2001. 011105.


Acrochordoidea:Wart or file snakes, Acrochordus. 

Range:

Like advanced snakes in mobility of jaw; primarily aquatic; scales parallel(?), secondarily(?) reduced ventral scales.

ATW991003.


checked ATW060222