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Ophiacodontidae Thien Nguyen CSUSB Biology 680 - 2009.

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Presentation on theme: "Ophiacodontidae Thien Nguyen CSUSB Biology 680 - 2009."— Presentation transcript:

1 Ophiacodontidae Thien Nguyen CSUSB Biology

2 Introduction Kingdom: Animalia Kingdom: Animalia Phylum: Chordata Phylum: Chordata Superclass: Tetrapoda Superclass: Tetrapoda Class: Synapsida Class: Synapsida Order: Pelycosauria Order: Pelycosauria Sub-Order: Ophiacodontia Sub-Order: Ophiacodontia Family: Ophiacodontidae Family: Ophiacodontidae

3 Ophiacodontia Ophiacodontidae Ophiacodontidae Which include pelycosaurs with features once considered as primitive and close to the basal stock of the order Which include pelycosaurs with features once considered as primitive and close to the basal stock of the order There is a fairly complete knowledge of Ophiacodontidae anatomy, particularly on Ophiacodon There is a fairly complete knowledge of Ophiacodontidae anatomy, particularly on Ophiacodon Members of the family include Members of the family include Archeothyris Archeothyris Clepsydrops Clepsydrops Ophiacodon Ophiacodon Varanosaurus Varanosaurus

4 Introduction Ophiacodonts first appeared in the late Carboniferous period. Ophiacodonts first appeared in the late Carboniferous period. Many were possibly semi- or fully aquatic animals. Many were possibly semi- or fully aquatic animals. They have piscivorous habits (feeding on fishes) and amphibious adaptations They have piscivorous habits (feeding on fishes) and amphibious adaptations Fed on food items which required little mastication; this is due to features such as their long snout, lightly built skulls and jaws, and undifferentiated dentitions Fed on food items which required little mastication; this is due to features such as their long snout, lightly built skulls and jaws, and undifferentiated dentitions

5 Ophiacodontia These animals had low and relatively broad skulls with a moderately elongated snout These animals had low and relatively broad skulls with a moderately elongated snout Concaved dorsal borders of the orbit Concaved dorsal borders of the orbit Lower margin of skull is nearly straight Lower margin of skull is nearly straight Occiput slants strongly forward dorsally Occiput slants strongly forward dorsally Slender marginal teeth Slender marginal teeth Canines are always distinct Canines are always distinct Palatal teeth present but Palatal teeth present but not greatly developed

6 Jaw articulation is almost in-line or on the same level as the row of teeth Jaw articulation is almost in-line or on the same level as the row of teeth The jaw is slender The jaw is slender Symphasis is confined for the most part to the dentary Symphasis is confined for the most part to the dentary Coronoid is elevated Coronoid is elevated Developed pterygoid flange (although not thickened) Developed pterygoid flange (although not thickened) Lacrimal reaches the naris Lacrimal reaches the naris Basal portion of quadrate Basal portion of quadrate is broad transversely

7 Vertebrae is primitively short but tends to elongate in some forms Vertebrae is primitively short but tends to elongate in some forms Presacral Centra tends to be flattened ventrally and keel in dorsal region is never sharp Presacral Centra tends to be flattened ventrally and keel in dorsal region is never sharp Transverse processes are short while the neural arch tends to be broad and heavy Transverse processes are short while the neural arch tends to be broad and heavy The cervical ribs are dialated The cervical ribs are dialated Abdominal ribs are highly developed Abdominal ribs are highly developed Clavicals are narrow distally and Clavicals are narrow distally and head of interclavical is short →

8 Scapula is short and broad Scapula is short and broad The Supraglenoid foramen occupies primitive position The Supraglenoid foramen occupies primitive position Coracoid does not lag in ossification Coracoid does not lag in ossification Process for coracoid head of the triceps is slightly developed Process for coracoid head of the triceps is slightly developed

9 The ilium is long but unexpanded dorsally but retains dorsal trough for axial muscle attachment The ilium is long but unexpanded dorsally but retains dorsal trough for axial muscle attachment Pubic tubercle is usually present Pubic tubercle is usually present Internal shelf for the puboishio- Internal shelf for the puboishio- femoralis internus is present on the pubis

10 Ophiacodontidae Features of the Skull Features of the Skull Always large and relatively narrow Always large and relatively narrow Moderately to greatly elongated facial region Moderately to greatly elongated facial region Numerous marginal teeth Numerous marginal teeth in upper jaw in upper jaw Moderately developed canines Moderately developed canines Stapes is a massive rod Stapes is a massive rod

11 Ophiacodontidae Physical features Physical features Short vertebrae Short vertebrae Hind legs are longer than the fore legs Hind legs are longer than the fore legs The atlas centrum doesn’t reach ventral surface of the column The atlas centrum doesn’t reach ventral surface of the column Primitive adductor ridge in femur has disappeared. Primitive adductor ridge in femur has disappeared. Caudal muscles have no prominent area for attachment Caudal muscles have no prominent area for attachment

12 Ophiacodontidae Members of the family include: Members of the family include: Ophiacodon Ophiacodon Varanosaurus Varanosaurus Clepsydrops Clepsydrops * These three are strikingly similar with only slight differences in their skull and vertebrae proportions and a few others.

13 Ophiacodon

14 Ophiacodon Ophiacodontids were generally moderate to very large in size Ophiacodontids were generally moderate to very large in size Skull is large, long, and high Skull is large, long, and high Vertebrae are more slender than smaller members of the family Vertebrae are more slender than smaller members of the family Pubic tubercle is reduced or absent Pubic tubercle is reduced or absent There is a development of a secondary adductor ridge on the femur There is a development of a secondary adductor ridge on the femur Unguals (or claws) are flattened Unguals (or claws) are flattened Ophiacodons have a distinctive feature in that they have slow ossification of replacement bones, both in the skull and postcranial skeleton Ophiacodons have a distinctive feature in that they have slow ossification of replacement bones, both in the skull and postcranial skeleton

15 Ophiacodon Greatly elongated skull (Due to elongated nasal, lacrimal, maxillae, frontal and pre-frontal elements) Greatly elongated skull (Due to elongated nasal, lacrimal, maxillae, frontal and pre-frontal elements) Disappearance of the palaeorbital connection of pre and postfrontals (a primitive feature) Disappearance of the palaeorbital connection of pre and postfrontals (a primitive feature) Moderately long post orbital region Moderately long post orbital region Lacrimal (L) is very thin Lacrimal (L) is very thin Lacrimal duct can extend as Lacrimal duct can extend as as far as level of canines Small supratemporal (ST) Small supratemporal (ST) Anterior margin of orbit is Anterior margin of orbit is thin ventrally and thickened dorsally

16 Parietal bone is a single structure. Although in some Ophiacodon and Varanosaurus specimens, the interparietal is divided in two by a longitudinal fissure Parietal bone is a single structure. Although in some Ophiacodon and Varanosaurus specimens, the interparietal is divided in two by a longitudinal fissure Debate as to whether it is a crack or suture Debate as to whether it is a crack or suture Slender connection between maxilla and premaxilla Slender connection between maxilla and premaxilla Ascending bar on inner surface of the maxilla (also present in Clepsydrops) above the canines; possibly to brace the tooth row to the skull roof Ascending bar on inner surface of the maxilla (also present in Clepsydrops) above the canines; possibly to brace the tooth row to the skull roof Post orbital (PO) and jugal (J) Post orbital (PO) and jugal (J) forms a broad bar extending medially behind the orbit Palate (PAL) is lightly built Palate (PAL) is lightly built

17 The quadratojugal is well developed and extends almost to the maxilla. It is also fused to the quadrate and has an articulation with pterygoid ramus above the quadrate foramen The quadratojugal is well developed and extends almost to the maxilla. It is also fused to the quadrate and has an articulation with pterygoid ramus above the quadrate foramen Squamosal (SQ) has a well-developed reflected lamina which provides an attachment to the tip of the paraoccipital process Squamosal (SQ) has a well-developed reflected lamina which provides an attachment to the tip of the paraoccipital process Choanae are long and narrow while prevomers are slender and toothless Choanae are long and narrow while prevomers are slender and toothless Row of teeth present which runs forward along the margin of the narrow interpterygoid vacuity Row of teeth present which runs forward along the margin of the narrow interpterygoid vacuity Second line of teeth runs along Second line of teeth runs along palatal ramus of the pterygoid

18 Articular area for the basipterygoid process is large and deep and is situated far ventrally Articular area for the basipterygoid process is large and deep and is situated far ventrally The stapes is situated on a cavity formed by the quadrate ramus of the pterygoid and the adjacent portion of the quadrate The stapes is situated on a cavity formed by the quadrate ramus of the pterygoid and the adjacent portion of the quadrate Quadrate (Q) is transversely expanded with its articular surface situated in a nearly horizontal plane Quadrate (Q) is transversely expanded with its articular surface situated in a nearly horizontal plane Its believed that the quadrate bone is built to aid the pterygoid in enclosing the middle ear chamber Its believed that the quadrate bone is built to aid the pterygoid in enclosing the middle ear chamber

19 Ophiacodon Braincase is adequately studied Ophiacodon Braincase is adequately studied The sutures between all of the braincase elements can be seen due to the slow ossification process in Ophiacodon The sutures between all of the braincase elements can be seen due to the slow ossification process in Ophiacodon Outline of supraoccipital is subquadrate Outline of supraoccipital is subquadrate Venous depression present on inner surface of supraoccipital Venous depression present on inner surface of supraoccipital The opisthotic (op) occupies the latero-ventral portion of the occipital plate and is clearly separable from the other elements The opisthotic (op) occupies the latero-ventral portion of the occipital plate and is clearly separable from the other elements Opisthotic is incompletely ossified ventrally at the area where it borders the fenestra ovalis Opisthotic is incompletely ossified ventrally at the area where it borders the fenestra ovalis

20 Jaw Jaw Slender and shallow dorso-ventrally at the anterior end Slender and shallow dorso-ventrally at the anterior end Symphysis of bones is weakly developed and primarily confined in the dentary Symphysis of bones is weakly developed and primarily confined in the dentary Dentary (D) is elongated Dentary (D) is elongated Oval external opening is present in between the dentary, angular, and subangular 1 Oval external opening is present in between the dentary, angular, and subangular 1 The postero-dorsal expansion of the Dentary covers much of the outer side of the surangular (SANG) The postero-dorsal expansion of the Dentary covers much of the outer side of the surangular (SANG) Maxillary (MX) region is slightly Maxillary (MX) region is slightlyconcaved Coronoid (C) region is slightly Coronoid (C) region is slightlyconvexed Upper margin of surangular Upper margin of surangular is thin

21 The angular has a prominent ventral keel The angular has a prominent ventral keel Splenial (SP) is broad on the internal surface but is barely visible from the outer view Splenial (SP) is broad on the internal surface but is barely visible from the outer view Prominent ventral keel present on articular (A) and is continuous with the angular; Internal processes for muscle attachments are not present on the articular Prominent ventral keel present on articular (A) and is continuous with the angular; Internal processes for muscle attachments are not present on the articular Articular surface is gently tilted inward and appear to be primitive in construction Articular surface is gently tilted inward and appear to be primitive in construction Both cavities are short antero- Both cavities are short antero-posterioly Lateral cavity is deeply concaved Lateral cavity is deeply concaved Medial cavity is flat Medial cavity is flat

22 Marginal teeth are rounded in section, sharply pointed, and slightly recurved Marginal teeth are rounded in section, sharply pointed, and slightly recurved The bases of each tooth are subquadrate and have longitudinal striations The bases of each tooth are subquadrate and have longitudinal striations Tooth replacement is believed to be slow, resulting in frequent gaps in the tooth row Tooth replacement is believed to be slow, resulting in frequent gaps in the tooth row Total number of maxillary teeth generally range from Total number of maxillary teeth generally range from precanines are always present 6-7 precanines are always present Canines are not very projecting but are distinct Canines are not very projecting but are distinct Dentary teeth are generally more numerous, crowded, and smaller in size Dentary teeth are generally more numerous, crowded, and smaller in size

23 Vertebrae Vertebrae There are generally 27 pre-sacral vertebrae, 2 sacrals, and an elongated tail present There are generally 27 pre-sacral vertebrae, 2 sacrals, and an elongated tail present The vertabrae and the body as a whole is short which is believed to be a primitive feature The vertabrae and the body as a whole is short which is believed to be a primitive feature Presence of 5 nonmovable ribs in front of the sacrum; possibly lumbars Presence of 5 nonmovable ribs in front of the sacrum; possibly lumbars

24 Transverse processes of the cervical and dorsal vertebrae are short (compared to other suborders) Transverse processes of the cervical and dorsal vertebrae are short (compared to other suborders) The dorsal transverse processes is semicircular in section The dorsal transverse processes is semicircular in section Posterior surface is flat while the anterior surface is convex Posterior surface is flat while the anterior surface is convex The arch of the transverse processes of the cervical emerges further down and slants sharply backwards and downwards The arch of the transverse processes of the cervical emerges further down and slants sharply backwards and downwards The dorsal neural spines are thin transversely and broad antero- posteriorly; cervical neural spines have stouter bases; spines in both cases have blunt tips and are never elongated The dorsal neural spines are thin transversely and broad antero- posteriorly; cervical neural spines have stouter bases; spines in both cases have blunt tips and are never elongated

25 Atlanto-axial complex indicate a common and distinctive structure Atlanto-axial complex indicate a common and distinctive structure Proatlas is present Proatlas is present Atlantal centrum may be fused with the axial intercentrum and is thick antero-posteriorly and has a well developed dorsal portion Atlantal centrum may be fused with the axial intercentrum and is thick antero-posteriorly and has a well developed dorsal portion Highly characteristic feature of Ophiacodontidae Highly characteristic feature of Ophiacodontidae Atlantal intercentrum is large and underlains the atalantal centrum Atlantal intercentrum is large and underlains the atalantal centrum Spine of axis expands antero- Spine of axis expands antero- posteriorly and is thin anteriorly and thickened at the posterior edge

26 The cervical ribs are two-headed and although lumbar ribs are present, they are often small The cervical ribs are two-headed and although lumbar ribs are present, they are often small Two sacrals are present Two sacrals are present The first sacral rib is large and has a fan shaped surface which fits into a hollow in the ilium The first sacral rib is large and has a fan shaped surface which fits into a hollow in the ilium The second rib is much smaller and has little contact w/the ilium; seems that its purpose was just to prop the first rib The second rib is much smaller and has little contact w/the ilium; seems that its purpose was just to prop the first rib Caudal ribs (approx. 11) were present and well developed Caudal ribs (approx. 11) were present and well developed

27 The blade of the clavicle is extremely narrow The blade of the clavicle is extremely narrow Shaft of clavicle is flattened and groove for attachment to the scapula is extremely underdeveloped Shaft of clavicle is flattened and groove for attachment to the scapula is extremely underdeveloped Distal ends are heavily striated Distal ends are heavily striated Believed that this is to compensate for the small area it has that contacts with the interclavicle Believed that this is to compensate for the small area it has that contacts with the interclavicle The bowl of the interclavical is The bowl of the interclavical is short and the anterior quadrants are only slightly developed; the blade is nearly uniform in width but broadens at mid-length

28 Scapulocoracoid Scapulocoracoid Scapular blade is generally low in correlation with the low build of the body Scapular blade is generally low in correlation with the low build of the body The scapula is broad; the posterior margin of scapula curves backwards to a slight degree The scapula is broad; the posterior margin of scapula curves backwards to a slight degree Coracoid surface below the glenoid is slightly concave in dorso- ventral section Coracoid surface below the glenoid is slightly concave in dorso- ventral section

29 Pelvic Girdle Pelvic Girdle Primitive in regards to the construction of the iliac blade Primitive in regards to the construction of the iliac blade Outer surface of ilium associated only with appendicular muscles Outer surface of ilium associated only with appendicular muscles Iliac blade is elongated and points posteriorly (which is believed to be a primitive feature); blade increases in height anteriorly Iliac blade is elongated and points posteriorly (which is believed to be a primitive feature); blade increases in height anteriorly Dorsal margin of iliac blade is characteristically concave in outline while it is convex posteriorly Dorsal margin of iliac blade is characteristically concave in outline while it is convex posteriorly Lower front margin of ilium forms a sharp ridge Lower front margin of ilium forms a sharp ridge Iliac component in the formation of Iliac component in the formation of the acetabulum is greatest in size Acetabulum has a thick posterior Acetabulum has a thick posteriormargin

30 Pelvic Girdle (cont.) Pelvic Girdle (cont.) Acetabulum is more dorsally facing (its deepest portion lies near the ischiadic component of the acetabulum Acetabulum is more dorsally facing (its deepest portion lies near the ischiadic component of the acetabulum Ischium points posteriorly Ischium points posteriorly The pubis is generally short; a thick dorsal margin descends sharply downward and outward from the acetabulum The pubis is generally short; a thick dorsal margin descends sharply downward and outward from the acetabulum In primitive forms, there is a prominent pubic tubercle In primitive forms, there is a prominent pubic tubercle Tubercle is reduced in Ophiacodon Tubercle is reduced in Ophiacodon The puboischiadic plate is relatively The puboischiadic plate is relatively narrow dorso-ventrally

31 Appendages Appendages Proximal segments of the limbs were short in comparison to the sphenacodontids or edaphosaurs Proximal segments of the limbs were short in comparison to the sphenacodontids or edaphosaurs Front legs are smaller than hind legs Front legs are smaller than hind legs Humerus was ~20% shorter than the femur; Humerus only ~10% shorter than femur in sphenacodontids and edaphosaurs Humerus was ~20% shorter than the femur; Humerus only ~10% shorter than femur in sphenacodontids and edaphosaurs Radius and ulna were noticeably shorter than tibia and fibula; These bones were approx. equal in size in sphenacodontids and edaphosaurs Radius and ulna were noticeably shorter than tibia and fibula; These bones were approx. equal in size in sphenacodontids and edaphosaurs

32 Humerus Humerus Articular surface occupies nearly the entire extent of the proximal end Articular surface occupies nearly the entire extent of the proximal end Anterior margin of supinator process curves out sharply beyond the middle of the humerus; distal surface is blunt and faces directly forward Anterior margin of supinator process curves out sharply beyond the middle of the humerus; distal surface is blunt and faces directly forward Supinator process positioned at a lower level than the ectepicondyle and is separated from it by a deep groove and notch Supinator process positioned at a lower level than the ectepicondyle and is separated from it by a deep groove and notch The proximal dorsal surface is The proximal dorsal surface is essentially flat The latissimus tubercle is small The latissimus tubercle is small

33 Humerus (cont.) Humerus (cont.) Surface for the coracobrachialis is tilted ventrally Surface for the coracobrachialis is tilted ventrally The deltopectoral crest is greatly developed; the proximal edge of the crest is thickened The deltopectoral crest is greatly developed; the proximal edge of the crest is thickened The radial articulation is nearly circular in outline The radial articulation is nearly circular in outline The radial and ulnar articulations combined occupies a relatively broad area along the distal end of the bone The radial and ulnar articulations combined occupies a relatively broad area along the distal end of the bone

34 Radius & Ulna Radius & Ulna The radius is very short and has less of an arch compared to those seen in spenacodonts; radius shaft is thick and convex dorsally in section The radius is very short and has less of an arch compared to those seen in spenacodonts; radius shaft is thick and convex dorsally in section A ridge is present not far below the head on the ventral side of the lateral margin A ridge is present not far below the head on the ventral side of the lateral margin Ridge slants out to the margin towards the distal end of the bone Ridge slants out to the margin towards the distal end of the bone Distal portion of the flexor surface is nearly flat Distal portion of the flexor surface is nearly flat The proximal articulation is semicircular The proximal articulation is semicircular The distal articulation is wide dorso- The distal articulation is wide dorso-ventrally

35 Like the radius, the ulna is also very short Like the radius, the ulna is also very short In general, the bone is flat dorso-ventrally In general, the bone is flat dorso-ventrally The lateral margin of the shaft has a rounded edge but becomes thin and ridge-like distally The lateral margin of the shaft has a rounded edge but becomes thin and ridge-like distally Dorsal surface of the head region is slightly concave Dorsal surface of the head region is slightly concave

36 Femur Femur The femur is short and nearly straight The femur is short and nearly straight Articular surface of the head is broad anteriorly Articular surface of the head is broad anteriorly The dorsal margin of the articular area is somewhat convex in outline The dorsal margin of the articular area is somewhat convex in outline The anterior tibial condyle flares out anteriorly to a moderate degree The anterior tibial condyle flares out anteriorly to a moderate degree Dorsal surface tilts strongly posteriorly Dorsal surface tilts strongly posteriorly The anterior margin descends abruptly into the intercondylar fossa The anterior margin descends abruptly into the intercondylar fossa

37 Femur (cont.) Femur (cont.) Intertrochanteric fossa is long, broad, and relatively shallow Intertrochanteric fossa is long, broad, and relatively shallow The ridge posterior to the intertrochanteric fossa is moderately developed The ridge posterior to the intertrochanteric fossa is moderately developed The popliteal area is flattened The popliteal area is flattened Tibial articular areas faces more distally than seen in other pelycosaurs; indicates that the knee was less flexible Tibial articular areas faces more distally than seen in other pelycosaurs; indicates that the knee was less flexible

38 Tibia & Fibula Tibia & Fibula Like the femur, the tibia and fibula are also short Like the femur, the tibia and fibula are also short The lateral area of the tibia head (area of articulation with the femur) is broad dorso-ventrally; this suggest that the articulation had limited rotation The lateral area of the tibia head (area of articulation with the femur) is broad dorso-ventrally; this suggest that the articulation had limited rotation The proximo-medial portion of the bone is thick with a rounded lateral margin; medial portion is broad and convex The proximo-medial portion of the bone is thick with a rounded lateral margin; medial portion is broad and convex The distal end of the shaft tends to curve laterally The distal end of the shaft tends to curve laterally

39 Head of fibula is narrow; pair of tubercles present, one below the other Head of fibula is narrow; pair of tubercles present, one below the other Articular areas for astragalus and calcaneum are elongated transversely and thin dorso-ventrally Articular areas for astragalus and calcaneum are elongated transversely and thin dorso-ventrally

40 Manus & Pes Manus & Pes Complete data available for Ophiacodon; data incomplete in Varanosaurus and only isolated elements are available for Clepsydrops Complete data available for Ophiacodon; data incomplete in Varanosaurus and only isolated elements are available for Clepsydrops Data on Manus and Pes seems to be consistent across the genera Data on Manus and Pes seems to be consistent across the genera Broadness of the feet suggest a webbed condition Broadness of the feet suggest a webbed condition The face on the radiale is larger than The face on the radiale is larger than that for the lateral centrale in the carpus Short contact between radiale Short contact between radiale and intermedium distally

41 Manus & Pes (cont.) Manus & Pes (cont.) The ulnare is nearly as broad as it is long The ulnare is nearly as broad as it is long Pisiform is elongated laterally Pisiform is elongated laterally Lateral centrale is relatively short; its breadth and length about equal Lateral centrale is relatively short; its breadth and length about equal Dorsal surface of the medial centrale is nearly smooth; Dorsal surface of the medial centrale is nearly smooth; Its articulation with the first distal Its articulation with the first distal carpal is relatively broad Has a small contact area with the Has a small contact area with the third distal carpal Primitive phalangeal formula retained Primitive phalangeal formula retained

42 Manus & Pes (cont.) Manus & Pes (cont.) The astragalus is nearly as broad as it is long The astragalus is nearly as broad as it is long Astragalus has a broad fibular facet; the proximal end of the bone is wide; upper half of the medial margin is thin and has a sharp edge Astragalus has a broad fibular facet; the proximal end of the bone is wide; upper half of the medial margin is thin and has a sharp edge Fibulare is broad; its length and width about equal Fibulare is broad; its length and width about equal Centralia have primitive characteristics; they have a subquadrate shape and are subequal in size Centralia have primitive characteristics; they have a subquadrate shape and are subequal in size Positioned side by side distal to the Positioned side by side distal to the astragalus and medial to the fourth distal tarsal Primitive phalangeal formula retained Primitive phalangeal formula retained

43 Varanosaurus

44 Skull Skull Skull is long and narrow; in lateral view, the dorsal margin is slightly concaved between the posterior margin of the naris and the midlength of the orbit Skull is long and narrow; in lateral view, the dorsal margin is slightly concaved between the posterior margin of the naris and the midlength of the orbit Ventral margin is slightly convex from tip of the snout to the level of the postorbital bar Ventral margin is slightly convex from tip of the snout to the level of the postorbital bar External naris divided into two opening by the septomaxilla External naris divided into two opening by the septomaxilla The naris is the larger orifice and position more anteriorly; it is subcircular in outline The naris is the larger orifice and position more anteriorly; it is subcircular in outline Posterior orifice has an outline of a right triangle; its function is unknown Posterior orifice has an outline of a right triangle; its function is unknown

45 The dorsal rim of the orbit is flattened and is subcircular in lateral view The dorsal rim of the orbit is flattened and is subcircular in lateral view Lateral temporal fenestra is located directly behind the orbit; bordered by the postorbital, squamosal, and jugal Lateral temporal fenestra is located directly behind the orbit; bordered by the postorbital, squamosal, and jugal Temp. fenestra has the outline of a right triangle w/rounded corners Temp. fenestra has the outline of a right triangle w/rounded corners

46 In dorsal view, the skull outline is narrow and triangular in shape In dorsal view, the skull outline is narrow and triangular in shape Dorsal skull table is nearly flat in transverse section Dorsal skull table is nearly flat in transverse section Orbits are semicircular notches in lateral margins of the skull table Orbits are semicircular notches in lateral margins of the skull table Antorbitally, the skull quickly narrows to about the midlength position of the nasals Antorbitally, the skull quickly narrows to about the midlength position of the nasals

47 In lateral view, the lower jaw is shallow and only slightly concave In lateral view, the lower jaw is shallow and only slightly concave A mandibular foramen is present on the lateral surface of the jaw located at the intersection of the dentary, angular, and surangular A mandibular foramen is present on the lateral surface of the jaw located at the intersection of the dentary, angular, and surangular Mandibular foramen is elongated and oval in shape and is positioned horizontally Mandibular foramen is elongated and oval in shape and is positioned horizontally A smaller opening (the Meckelian fenestra) is present on the medial surface of the jaw A smaller opening (the Meckelian fenestra) is present on the medial surface of the jaw

48 The premaxilla is small and lightly built; It has room for 6 teeth The premaxilla is small and lightly built; It has room for 6 teeth First 3 teeth are the largest and subequal in size, 4 th & 5 th are smaller and subequal, and the 6 th is the smallest First 3 teeth are the largest and subequal in size, 4 th & 5 th are smaller and subequal, and the 6 th is the smallest Dorsal surface of premaxilla is long and narrow Dorsal surface of premaxilla is long and narrow The nasal is relatively long; accounts for ~50% of the midline length of the skull roof; bone width remains relatively constant anteriorly The nasal is relatively long; accounts for ~50% of the midline length of the skull roof; bone width remains relatively constant anteriorly Frontals are exposed on the skull table and are subrectangular in shape Frontals are exposed on the skull table and are subrectangular in shape Lacrimal is long and narrow Lacrimal is long and narrow

49 Prefrontal forms the entire anterodorsal margin of the orbit Prefrontal forms the entire anterodorsal margin of the orbit Postfrontal forms the posterodorsal rim of the orbit Postfrontal forms the posterodorsal rim of the orbit Ventral end of orbital margin continues as a narrow ventral process along anterior wall of the orbit and medial to the orbital margin of the lacrimal Ventral end of orbital margin continues as a narrow ventral process along anterior wall of the orbit and medial to the orbital margin of the lacrimal In lateral view, the anterior margin of the prefrontal ends in a short and nearly vertical contact with the nasal bone In lateral view, the anterior margin of the prefrontal ends in a short and nearly vertical contact with the nasal bone Postfrontal bone is in the shape of an equilateral triangle Postfrontal bone is in the shape of an equilateral triangle

50 The maxilla has approx 55 teeth and tooth spaces; ventral margin of the anterior end of maxilla exhibits a step-like expansion where the first 14 teeth are located (ending with the larger caniniform tooth pair) The maxilla has approx 55 teeth and tooth spaces; ventral margin of the anterior end of maxilla exhibits a step-like expansion where the first 14 teeth are located (ending with the larger caniniform tooth pair) Anteriorly, the precaniniforms exhibit a steady decrease in size Anteriorly, the precaniniforms exhibit a steady decrease in size The anterior 8 postcaniniform teeth are slightly smaller than the last precaniniform tooth; followed by 8 slightly larger teeth (subequal in size) than the last precaniniform tooth; remainder of teeth gradually decreases in size posteriorly The anterior 8 postcaniniform teeth are slightly smaller than the last precaniniform tooth; followed by 8 slightly larger teeth (subequal in size) than the last precaniniform tooth; remainder of teeth gradually decreases in size posteriorly Teeth have sharply pointed tips are weakly curved posteriorly Teeth have sharply pointed tips are weakly curved posteriorly

51 Palate Palate Vomer is very narrow and forms almost all of the medial margin of the internal naris except for a small anterior portion which is formed by a posteriorly-directed vomerine process of the premaxilla Vomer is very narrow and forms almost all of the medial margin of the internal naris except for a small anterior portion which is formed by a posteriorly-directed vomerine process of the premaxilla A single row of small teeth is located close to and parallel with the medial margin of the ventral surface of the posterior half of the vomer A single row of small teeth is located close to and parallel with the medial margin of the ventral surface of the posterior half of the vomer

52 Anteriorly, the palatine overlaps dorsally the vomer for a short distance Anteriorly, the palatine overlaps dorsally the vomer for a short distance Ectopterygoids are present and are narrowly trapezoidal in outline Ectopterygoids are present and are narrowly trapezoidal in outline The pterygoid has a standard primitive amniote form, which consist of an anterior (palatal) ramus, transverse flange, and a posterior quadrate ramus The pterygoid has a standard primitive amniote form, which consist of an anterior (palatal) ramus, transverse flange, and a posterior quadrate ramus Although this part of the palate is incomplete, it is believed that the pterygoid does not reach the Although this part of the palate is incomplete, it is believed that the pterygoid does not reach the internal narial border The small interpterygoid vacuity The small interpterygoid vacuity has the outline of a narrow spade

53 Small teeth (appox. 0.06mm in diameter) are distributed over most of the palatal ramus except in two areas; one area is a narrow anteroposterior strip near the medial margin and the other is a triangular region anterior to the transverse process Small teeth (appox. 0.06mm in diameter) are distributed over most of the palatal ramus except in two areas; one area is a narrow anteroposterior strip near the medial margin and the other is a triangular region anterior to the transverse process Transverse flange supports a single row of ~10 teeth Transverse flange supports a single row of ~10 teeth Size of teeth gradually increases medially Size of teeth gradually increases medially Base of each tooth tends to be anteroposteriorly oval Base of each tooth tends to be anteroposteriorly oval

54 Mandible Mandible Dentary is the dominant element in lateral view; accounts for ~ 75% of the mandibular length Dentary is the dominant element in lateral view; accounts for ~ 75% of the mandibular length Posterior end forms the anterior half of the external mandibular foramen Posterior end forms the anterior half of the external mandibular foramen Dorsal margin continues posterodorsally on the lateral surface of the surangular where it ends as a short, spike-like process Dorsal margin continues posterodorsally on the lateral surface of the surangular where it ends as a short, spike-like process Dentary has ~60 or more tooth positions with tooth morphology similar to that seen in the upper jaw (sharply pointed tips and weakly curved); fewer size variation in teeth than seen in upper jaw Dentary has ~60 or more tooth positions with tooth morphology similar to that seen in the upper jaw (sharply pointed tips and weakly curved); fewer size variation in teeth than seen in upper jaw Teeth with the greatest height Teeth with the greatest height were located at about the midlength of the dentary and decreases in size anteiorly and posteriorly

55 In lateral view, the angular has a large, horizonatally oval exposure on the posteroventral angle In lateral view, the angular has a large, horizonatally oval exposure on the posteroventral angle Angular forms the posterior half of the ventral margin of the external mandibular foramen before continuing anteriorly under the dentary; it has a spike-like process posterodorsally Angular forms the posterior half of the ventral margin of the external mandibular foramen before continuing anteriorly under the dentary; it has a spike-like process posterodorsally The entire dorsal margin of the angular behind the external mandibular foramen contacts the surangular The entire dorsal margin of the angular behind the external mandibular foramen contacts the surangular Surangular forms a low, flat spike-like extension anterodorsally Surangular forms a low, flat spike-like extension anterodorsally

56 In medial view, the splenial is the dominant element, covering the entire anterior half of the jaw In medial view, the splenial is the dominant element, covering the entire anterior half of the jaw As posterior end of splenial tapers to the ventral margin of the jaw, it contacts the narrow anterior end of the posterior coronoid, then broadly contacts the prearticular and angular As posterior end of splenial tapers to the ventral margin of the jaw, it contacts the narrow anterior end of the posterior coronoid, then broadly contacts the prearticular and angular The long and narrow prearticular forms the broadly concave ventral border of the adductor fossa then continues anteriorly where it wedges between the posterior coronoid and splenial The long and narrow prearticular forms the broadly concave ventral border of the adductor fossa then continues anteriorly where it wedges between the posterior coronoid and splenial Near the posterior end of the prearticular, it expands dorsally into a broadly triangular flange that underlies the articular Near the posterior end of the prearticular, it expands dorsally into a broadly triangular flange that underlies the articular

57 Braincase Braincase Exoccipitals and basioccipital bones remain as distinct bones Exoccipitals and basioccipital bones remain as distinct bones The supraoccipital is thick and massive; it extends outward and forward medially to form wing-like expansions; its ventrolateral corner forms the medial wall and ventral floor of the posttemporal fenestra The supraoccipital is thick and massive; it extends outward and forward medially to form wing-like expansions; its ventrolateral corner forms the medial wall and ventral floor of the posttemporal fenestra Supraocciptal continues a short distance anterodorsally beneath the postparietals Supraocciptal continues a short distance anterodorsally beneath the postparietals A great portion of the lateral walls A great portion of the lateral walls of the braincase is formed by the prootics

58 The basisphenoid and parasphenoid fuse to form the basiparasphenoid complex which expands laterally in the posterior region The basisphenoid and parasphenoid fuse to form the basiparasphenoid complex which expands laterally in the posterior region The basipterygoid processes appear as stout, subrectangular plugs which ventrolaterally and slightly anteriorly The basipterygoid processes appear as stout, subrectangular plugs which ventrolaterally and slightly anteriorly

59 Stapes Stapes Stapes is similar to that seen in ophiacodon but relatively smaller in size (particularly the length of the shaft) Stapes is similar to that seen in ophiacodon but relatively smaller in size (particularly the length of the shaft) The footplate of the stapes is large and roughly oval in shape; it is narrow ventrally and broadly rounded dorsally The footplate of the stapes is large and roughly oval in shape; it is narrow ventrally and broadly rounded dorsally Shaft is slightly thicker ventrally than dorsally and runs ventrolaterally and posteriorly to reach the quadrate Shaft is slightly thicker ventrally than dorsally and runs ventrolaterally and posteriorly to reach the quadrate The distal end of the shaft fits into a recess in the quadrate but falls short of the floor of the recess; this suggest that there is a cartilaginous continuation The distal end of the shaft fits into a recess in the quadrate but falls short of the floor of the recess; this suggest that there is a cartilaginous continuation The dorsal process of the stapes The dorsal process of the stapes contacts the underside of the tabular lateral to the tabular- supraoccipital contact

60 Vertabrae Vertabrae *There are many similarities between Ophiacodon and Varanosaurus but the characteristics that define Varanosaurus can be seen in the vertebral column There are presacral vertebrae (which includes the atlas and axis) and 2 sacral vertabrae of the axial skeleton There are presacral vertebrae (which includes the atlas and axis) and 2 sacral vertabrae of the axial skeleton The atlantal centrum and axial intercentrum fuse to form the Atlanto-axial complex The atlantal centrum and axial intercentrum fuse to form the Atlanto-axial complex Degree of fusion between the elements may be due to maturity rather than taxonomic distinction; Complex probably not seen in juveniles Degree of fusion between the elements may be due to maturity rather than taxonomic distinction; Complex probably not seen in juveniles The plane of fusion between the elements runs posteroventrally which is a direction opposite to that seen in ophiacodon (posterodorsally) The plane of fusion between the elements runs posteroventrally which is a direction opposite to that seen in ophiacodon (posterodorsally)

61 There are small parapophyseal articulation for the axial ribs present on the axial intercentrum which are thinner and narrower than those in ophiacodon There are small parapophyseal articulation for the axial ribs present on the axial intercentrum which are thinner and narrower than those in ophiacodon The atlantal neural arch is composed of two elements that did not fuse dorsally; ventromedial facets articulate with the anterior edge of the atlantal centrum The atlantal neural arch is composed of two elements that did not fuse dorsally; ventromedial facets articulate with the anterior edge of the atlantal centrum Wing-like processes on the neural arches are smaller in size than those in ophiacodon Wing-like processes on the neural arches are smaller in size than those in ophiacodon No dorsally directed neural spine present in varanosaurus No dorsally directed neural spine present in varanosaurus

62 The axial centrum has a shallow but well-defined ventral keel The axial centrum has a shallow but well-defined ventral keel A horizontally directed ridge runs from the posterior limit of each transverse process back to the ridge of the centrum A horizontally directed ridge runs from the posterior limit of each transverse process back to the ridge of the centrum The pedicle of the neural arch is defined by a posterior constriction located just above the transverse processes The pedicle of the neural arch is defined by a posterior constriction located just above the transverse processes

63 Dorsal Vertebrae Dorsal Vertebrae Dorsal centra are amphicoelous (concave on both sides) Dorsal centra are amphicoelous (concave on both sides) Anterior and posterior ends are slightly tapered at ventral portion for the reception of a small intercentra Anterior and posterior ends are slightly tapered at ventral portion for the reception of a small intercentra The articular facets of the anterior zygopophyses are tilted ventromedially (~20 o to the horizontal plane) where as those of the posterior zygopophyses are angled dorsolaterally (~15 o ) The articular facets of the anterior zygopophyses are tilted ventromedially (~20 o to the horizontal plane) where as those of the posterior zygopophyses are angled dorsolaterally (~15 o ) Posterior vertebrae appear to be more tightly articulated at both the anterior and posterior zygopophyses than those of the anterior vertebrae Posterior vertebrae appear to be more tightly articulated at both the anterior and posterior zygopophyses than those of the anterior vertebrae

64 Transverse processes are well developed especially in the 6 th and 7 th presacrals where its length is nearly ¾ the width of its centrum Transverse processes are well developed especially in the 6 th and 7 th presacrals where its length is nearly ¾ the width of its centrum Neural arches seen in varanosaurus differs from that seen in the other members of the family Neural arches seen in varanosaurus differs from that seen in the other members of the family Neural arches of the 3 rd & 4 th presacrals are similarly proportioned Neural arches of the 3 rd & 4 th presacrals are similarly proportioned The 5 th & 6 th neural arches are wider while the 7 th, 8 th, and so forth are distinctively “swollen” The 5 th & 6 th neural arches are wider while the 7 th, 8 th, and so forth are distinctively “swollen” There is an alternation in height of the neural spines in some regions of the vertebral column (mid-column) There is an alternation in height of the neural spines in some regions of the vertebral column (mid-column) A feature known in a variety of Late Paleozoic tetrapods A feature known in a variety of Late Paleozoic tetrapods

65 Shorter or low spines are narrow transversely and elongated anteroposteriorly Shorter or low spines are narrow transversely and elongated anteroposteriorly Bases of the spines are long and narrowly subrectangular in outline Bases of the spines are long and narrowly subrectangular in outline Shorter spines include presacrals 5, 8, 12, 14, 16, 19, and 22 Shorter spines include presacrals 5, 8, 12, 14, 16, 19, and 22 In lateral view, the taller spines are trapezoidal or conical and angled slightly posteriorly In lateral view, the taller spines are trapezoidal or conical and angled slightly posteriorly Bases of the spines are oval in outline Bases of the spines are oval in outline Tall spines include those not listed above Tall spines include those not listed above Presacrals 20 and are unknown because the vertebrae or the spines are missing Presacrals 20 and are unknown because the vertebrae or the spines are missing

66 Sacral Vertebrae and Sacral Ribs Sacral Vertebrae and Sacral Ribs Two Sacrals are present in vertebral column Two Sacrals are present in vertebral column They are more robustly constructed than all of the presacral vertebrae and are also generally shorter in length They are more robustly constructed than all of the presacral vertebrae and are also generally shorter in length The neural arches continue smoothly up to sharp, narrow neural spines which do not have any pattern of height alternation seen in the presacral column The neural arches continue smoothly up to sharp, narrow neural spines which do not have any pattern of height alternation seen in the presacral column A ridge is present in the second sacral vertebrae which runs parallel to the anterior margin A ridge is present in the second sacral vertebrae which runs parallel to the anterior margin The proximal portion of the first sacral rib extends laterally for a short distance and then angles The proximal portion of the first sacral rib extends laterally for a short distance and then angles downwards; the distal portion of the rib expands broadly to form a fan-shaped surface

67 Anterior edge of first sacral rib turns sharply towards a vertical plane Anterior edge of first sacral rib turns sharply towards a vertical plane Distal portion of second sacral rib is not as broadly expanded as the first but is thicker dorsoventrally Distal portion of second sacral rib is not as broadly expanded as the first but is thicker dorsoventrally The distal expansions of both sacral ribs lay close to the horizontal plane The distal expansions of both sacral ribs lay close to the horizontal plane

68 Caudal Vertebrae and Caudal Ribs Caudal Vertebrae and Caudal Ribs The 3 caudals following the sacral complex show little decrease in size and proportion; spines of these caudals appear to be narrow The 3 caudals following the sacral complex show little decrease in size and proportion; spines of these caudals appear to be narrow The base of the tail is relatively thick; the proximal caudal vertebrae is stoutly built and lacked expanded neural arches The base of the tail is relatively thick; the proximal caudal vertebrae is stoutly built and lacked expanded neural arches Central length of the caudal does not change much by the middle of the tail but the transverse measure decreases substantially Central length of the caudal does not change much by the middle of the tail but the transverse measure decreases substantially Haemal arches are clearly present beyond the 7 th caudal; in addition, the articular surfaces Haemal arches are clearly present beyond the 7 th caudal; in addition, the articular surfaces of the transverse processes are circular in outline Haemal arches reach as far back Haemal arches reach as far back as the 30 th caudal

69 By the middle of the tail, the centra are narrower; neural arches are less built with shallow excavations at their bases By the middle of the tail, the centra are narrower; neural arches are less built with shallow excavations at their bases The posteriormost portion of the tail retains approximately the same length as the cauduals anterior to the section The posteriormost portion of the tail retains approximately the same length as the cauduals anterior to the section Neural arches and spines still persist as distinct structures even in the posteriormost portion of the tail; transverse processes cannot been seen in this portion Neural arches and spines still persist as distinct structures even in the posteriormost portion of the tail; transverse processes cannot been seen in this portion

70 References Berman, D. S, R. R. Reisz, J. R. Bolt, and D. Scott The cranial anatomy and relationships of the synapsid Varanosaurus (Eupleycosauria: Ophiacodontidae) from the Early Permian of Texas and Oklahoma. Annals of Carnegie Museum, 64: Berman, D. S, R. R. Reisz, J. R. Bolt, and D. Scott The cranial anatomy and relationships of the synapsid Varanosaurus (Eupleycosauria: Ophiacodontidae) from the Early Permian of Texas and Oklahoma. Annals of Carnegie Museum, 64: Palaeos.com Palaeos.com Romer, A.S. and L. I. Price Review of the Pelycosauria. Bulletin of the Geological Society of America Special Papers, 28: Romer, A.S. and L. I. Price Review of the Pelycosauria. Bulletin of the Geological Society of America Special Papers, 28: Sumida, S. S Reinterpretation of vertebral structure in the Early Permian pelycosaur Varanosaurus acutirostris (Amniota, Synapsida). Journal of Vertebrate Paleontology, 9: Sumida, S. S Reinterpretation of vertebral structure in the Early Permian pelycosaur Varanosaurus acutirostris (Amniota, Synapsida). Journal of Vertebrate Paleontology, 9:


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