Oraristrix brea ( Howard, 1933 ), 2010

Campbell, Kenneth E. & Bocheński, Zbigniew M., 2010, A New Genus for the Extinct Late Pleistocene Owl Strix brea Howard (Aves: Strigiformes) from Rancho La Brea, California, Records of the Australian Museum 62 (1), pp. 123-144 : 125-137

Oraristrix brea ( Howard, 1933) ,

new combination

Strix brea Howard, 1933 , (March 17), Condor 35(2), p. 66, fig. 15 [sic].

Figs 1 , 4–6 , 8

Types. HOLOTYPE, complete left tarsometatarsus, LACM RLB E9379 . PARATYPES: Rancho La Brea : 8 complete right and 9 complete left tarsometatarsi; 1 proximal right and 1 distal left tarsometatarsus .

Referred material. Rancho La Brea: Rostrae maxillare, 2; mandible, 1 anterior with symphysis; sternae, 3; scapulae, 5 right, 9 left; coracoids, 5 complete and 1 scapular end right, 4 complete and 2 scapular ends left; clavicula, 1 right dorsal end; humeri, 3 complete right and 2 complete left, 1 proximal right and 2 proximal left, 1 distal right and 2 distal left; ulnae, 1 complete right, 3 proximal right and 2 proximal left, 2 distal right and 2 distal left; radii, 5 proximal left, 2 distal right and 2 distal left; carpometacarpi, 7 complete right and 4 complete left, 2 distal right; femora, 2 complete right and 3 complete left, 2 proximal left, and 5 distal right and 5 distal left; tibiotarsi, 2 complete right and 3 complete left, 1 proximal right and 5 proximal left, 9 distal right and 3 distal left; fibulae, 3 proximal left; pelves, 2. For catalogue numbers, see Appendix 1.

Carpinteria. Locality LACM (CIT) 139: Rostrum maxillare, 1; coracoids, 1 right and 1 left; humeri, 1 complete left and 1 proximal left; carpometacarpus, 1 incomplete left; tarsometatarsus, 1 complete left. Collections of Santa Barbara Museum of Natural History: Coracoid, sternal end, left; tibiotarsus, distal, right.

Emended diagnosis. As for genus.

Type locality and horizon. Asphalt deposits of Rancho La Brea, at a depth of 3.7–4.9 m (12–16 feet) in Pit 16, Los Angeles , California .

Age. Late Pleistocene.

Description. Oraristrix brea was approximately the same size overall as modern Bubo virginianus and Strix nebulosa , but it was far larger than both S. varia and S. occidentalis , as noted by Howard (1933). In general, the bones of O. brea are more slender, or more lightly built, than those of both B. virginianus and S. nebulosa , although some elements are more robust in some measurements. Oraristrix brea also differs in its limb proportions from those species. Thus, in addition to the diagnostic osteological characters, differences between Oraristrix , Strix , and Bubo are apparent in both intra- and inter-element and intermembral proportions (see, e.g., Figs 2 , 3 ). For measurements of all elements, see Table 1.

Tarsometatarsus ( Figs 1A–G , 2 , 3 ). This bone was discussed in greater detail than any other by Howard (1933), who described five morphological characters and a number of ratios differentiating the extinct species from Strix occidentalis , S. varia , and Bubo virginianus . Our characters 1, 2, 3, and 9 above are four of these characters that we found to hold up well with our larger comparative series of modern species. However, we found that Howard’s (1933:66) distinguishing character 2 (“distal margin of this surface [i.e., posterior, or plantar, surface of internal calcaneal ridge] (as seen in lateral view) sharply defined from portion of calcaneal ridge immediately distal to it, even overhanging”) did not consistently distinguish Oraristrix brea .

Rostrum maxillare ( Fig. 4A–C ). Characterized by having (1) Os nasale with posterior edge sloping steeply anteriad, in lateral view [sloping significantly less steeply in Bubo (except in Nyctea where slope is similar to that of Oraristrix ) and Strix ]; (2) Fossae nasales with long axis at steeper angle to Crista tomialis than in either Bubo or Strix ; (3) Fossae nasales with internal floor deeply excavated, nearly parallel to tomial margin (floor of nares similar in Bubo ; much less excavated in Strix ); (4) Crista tomialis extends posteriad ventral to, and separated from, Proc. jugalis for a significant distance, ending as pointed projection (similar to shorter in Bubo ; extends posteriad under Proc. jugalis only slightly, if any, in Strix ).

Howard’s (1933) only criterion for distinguishing the Rostra maxillare of Oraristrix from the many partial Bubo specimens in the collection (i.e., turbinates more widely [ Figure 3 . continued from facing page] … each symbol represents one specimen, whereas for Oraristrix brea and fossil Bubo virginianus from Rancho La Brea the symbol stands for the arithmetic means of all fossil specimens of particular elements. For O. brea the number of fossil specimens available for calculating the means was as follows: humerus, 4; coracoid, 10; carpometacarpus, 7; femur, 5; tibiotarsus, 5; tarsometatarsus, 15. For fossil B. virginianus , the number of specimens available for calculating the means was as follows: humerus, 6; ulna, 6; carpometacarpus, 34; femur, 41; tibiotarsus, 18; tarsometatarsus, 68.

separated in median line anteriorly, which we interpret as in ventral view through Concavitas maxillare) is valid for separating the Brea Owl from Bubo virginianus and allying it with the traditional species of Strix . That is, the turbinates are similar, or even less inflated in Strix and markedly more inflated in Bubo . However, available species of Ciccaba , a genus now included in Strix , have well inflated anterior turbinates. On the other hand, the anterior turbinates of Nyctea , a genus now included in Bubo , are not inflated. Although the Rostra maxillare of all large owl specimens in the Rancho La Brea collections are damaged, most of them preserve the anterior parts of the turbinates and some or all of the other characters mentioned above, and they are identifiable as either Bubo or Oraristrix .

It is interesting to note that the Rostrum maxillare of Oraristrix brea was nearly as tall and long as that of the living Eurasian Eagle-owl, Bubo bubo , which is much larger than B. virginianus , but it was noticeably narrower ( Table 1). What this might indicate about its predatory habits is unclear, but it was a strong predator.

Sternum ( Fig. 4D–F ). Characterized by having (1) Linea intermusculare beginning at Tub. labri externi or posterior to it (similar in Strix ; Linea intermusculare begins medial and anterior to Tub. labri externi in Bubo ) ( Howard, 1933); (2) Tub. labrum externi not projecting greatly laterad, resulting in only slight to moderate curvature toward midline of Labrum externi and a shallow Sulci artic. coracoideus dorsal to Tub. labrum externi (Tub. labrum externi projecting more laterad, resulting in slight to moderate curvature to Labrum externi in Strix and much greater curvature in Bubo , and a deep to very deep Sulci artic. coracoideus dorsal to Tub. labrum externi in both Strix and Bubo ); (3) Corpus sternae with Margo posterior pointed, or arrow-shaped, and with Carina sterni extending to tip (Margo posterior of sternum in Strix squared off or slightly rounded, moderately wide, with Carina sterni merging before posterior end; Margo posterior of sternum in Bubo squared off or centrally notched, moderately wide to wide, with Carina sterni merging before posterior end). The three fossil sternae are too fragmentary to secure many accurate measurements, and minor breakage to Margo posterior of Corpus sternae might have accentuated its pointed form.

Clavicula ( Fig. 4R ). Characterized by having (1) Fac. artic. acrocoracoidea a moderately deep, elongated oval facing posterolaterad (facet more elongated than oval, less concave, and facing more posteriad in Strix ; facet more oval, moderately deep, and facing more posteriad in Bubo ); (2) Fac. artic. procoracoidea small, narrow, not well marked (facet much broader and well marked in Strix and Bubo ); (3) Extremitas omalis claviculae short (long in Strix and Bubo ).

Scapula ( Fig. 4G–J ). Characterized by having (1) acromion short, blunt-ended, and overall stout (i.e., wider dorsoventrally), in dorsolateral view (acromion much longer, narrower, and slightly less rounded anteriorly in Bubo ; short to long, narrower, and more pointed anteriorly in Strix ) ( Howard, 1933); (2) Fac. artic. humeralis (glenoid facet) with ventral edge moderately rounded, in medial view (ventral edge nearly straight in Bubo ; slightly to moderately rounded in Strix ); (3) Fac. artic. humeralis more rounded than elongated (glenoid facet rounded to elongated in Strix and more elongated in Bubo ); (4) medial surface just posterior to acromion markedly concave with long, prominent, narrow ridge marking dorsomedial corner of bone (area with shallow, elongated depression with long, sharp ridge narrowing posteriad in Strix ; area with shallow depression and with short to moderately long, prominent ridge narrowing rapidly posteriad in Bubo ). Characters (2) and (3) were combined by Howard (1933:68) when she referred to the glenoid facet of Oraristrix brea as “appearing more ‘heart-shaped’ than Bubo …, resembling Strix in this character…”.

Coracoid ( Fig. 4M–O ). Characterized by having (1) Proc. acrocoracoideus claviculae (anterior end, in ventral view) broad, narrowing sharply at Fac. artic. clavicularis [Proc. acrocoracoideus claviculae broad, narrowing slightly via curvature at Fac. artic. clavicularis in Strix (excluding Ciccaba , where it widens slightly at Fac. artic. clavicularis); Proc. acrocoracoideus claviculae broad, narrowing gradually in Bubo (excluding Nyctea , where it narrows more abruptly, but less so than in Oraristrix ) ( Howard, 1933); (2) Fac. artic. clavicularis relatively long, narrow, oriented at a slight angle to the long axis of shaft (shorter to long, a relatively narrow oval, oriented at a slightly greater angle to the long axis of shaft in Strix ; elongated oval to broad oval, not oriented at angle to long axis of shaft in Bubo ); (3) Proc. procoracoideus with terminus irregularly shaped, with broadened ventral half hosting a small Fac. artic. clavicularis posterior (Fac. artic. clavicularis elongated, blunt, and covering the entire end of a broad, oval Proc. procoracoideus in Strix and Bubo ); (4) shaft ventrolateral to Fac. artic. humeralis gently rounded (shaft more convex in this area in Strix and Bubo ) ( Howard, 1933); (5) Fac. artic. sternalis shallow, or narrow, in sternal view, extending mediad beyond tip of Angulus medialis (Fac. artic. sternalis moderately deep to deep in Strix and Bubo , in sternal view, not extending mediad beyond tip of Angulus medialis); (6) Angulus medialis near 90 degrees, in ventral view (Angulus medialis, in ventral view, moderately to very angular in Strix and very angular in Bubo ); (7) Linea intermusculare ventralis directly in line with Angulus lateralis of Fac. artic. sternalis (similar in Strix ; Linea intermusculare ventralis positioned medial to Angulus lateralis of Fac. artic. sternalis in Bubo ).

Howard (1933) described the pneumatization of the Proc. acrocoracoideus claviculae as being less pronounced in Oraristrix brea than in Strix or Bubo . We found this character to be quite variable, even within individuals, and we do not consider it a valid distinguishing character. Character 4 above (from Howard, 1933) is difficult to identify, and it is probably not a readily distinguishing character.

Humerus ( Fig. 5A–C ). Characterized by having (1) Caput humeri prominently developed ventral to Tub. dorsale (less developed in Strix and Bubo ); (2) Sulcus ligamentum transversus shallow, not extending ventrad past ventral edge of Incisura capitis (extends ventrad as moderately deep groove past ventral edge of Incisura capitis in Strix ; extends ventrad as a deep groove to well past ventral edge of Incisura capitis in Bubo ); (3) Crista bicipitalis, in anterior view, short and not extending past ventral edge of Tub. ventrale (long and similar, or extending slightly past ventral edge of Tub. ventrale, in Strix ; long and extending slightly to well past ventral edge of Tub. ventrale in Bubo ); (4) Epicondylus dorsalis with prominent spur proximal to proximal end of Condylus dorsalis (similar to very prominent spur at, or just proximal to, proximal end of Condylus dorsalis in Strix ; very prominent spur, proximal to proximal end of Condylus dorsalis in Bubo ).

Although Howard (1933) noted a somewhat larger Foramen pneumaticum in Strix than in Bubo , we found too much variability in this character to consider it reliable. We could not discern the “difficult to describe” differences in form of the attachment of M. brachialis mentioned by Howard (1933:68).

Ulna ( Fig. 6A–D ). Characterized by having (1) olecranon short, or moderately produced proximad, without proximal end turning ventrad, in anterior view (olecranon short in Strix , but with proximal end turning ventrad; olecranon moderate to long in Bubo , with proximal end turning ventrad); (2) Tub. lig. coll. ventralis relatively close to rim of Cotyla ventralis (moderate to large distance from rim of Cotyla ventralis in Strix and Bubo ). Howard (1933) did not describe the ulna of Oraristrix brea .

Radius ( Fig. 5F–I, L–N ). Characterized by (1) attachment for M. biceps brachii large, located mostly on posterior side of shaft at a moderate distance from Cotyla humeralis (similar in size, positioned more dorsally, or externally, on brea suggests that this bone had a stout distal end in comparison with that of Bubo virginianus ,

with some overlap with that of Strix nebulosa .

shaft and farther from Cotyla humeralis in Bubo ; attachment area similar in size but with external rim significantly larger, positioned more toward dorsal side of shaft, and at a greater distance from Cotyla humeralis in Strix ); (2) Cotyla humeralis narrow and elongated (broader and more oval in Bubo and Strix ); (3) distal end with Tub. aponeurosis ventralis short and distinctly set off from edge of shaft, in dorsal view [more elongated and slightly less distinctly set off from edge of shaft in Strix ; more elongated and not distinctly set off from edge of shaft (i.e., connected to edge of shaft by a long curve) in Bubo ]. Howard (1933) did not describe the radius of Oraristrix brea .

Carpometacarpus ( Figs 5O–P , 7 ). Characterized by having (1) Fac. artic. ulnocarpalis of Trochlea carpalis with ventral portion relatively narrow for length, moderately inflated posterodistally, in posterior view (wider and more inflated posterodistally in Strix and Bubo ); (2) Fac. artic. ulnocarpalis of Trochlea carpalis with posterodistal rim fairly straight, in dorsal view (Fac. artic. ulnocarpalis with posterodistal rim rounded and extending farther posteriad in Strix and Bubo ); (3) Tuberositas metacarpi majoris rounded in anterior view, distinctly set off from shaft proximally (rounded to triangular in Strix , less distinctly set off from shaft proximally; triangular shaped in Bubo , less distinctly set off from shaft proximally); (4) Os metacarpale minus with a distinct ridge for attachment of M. interosseous ventralis distally (ridge present, but sometimes interrupted in places in Strix ; ridge absent in Bubo ) (modified from Howard, 1933); (5) Fac. artic. digitalis minor long, dorsoventrally (relatively slightly longer and more slender in Strix ; shorter and more robust, or broader, in Bubo ); (6) area anteroproximal to Fac. artic. digitalis minor (i.e., proximal dorsal symphyseal area between Os metacarpale minus and Os metacarpale majus) flattened, in dorsal view (relatively flattened in Strix ; narrower and more convex in Bubo ) ( Howard, 1933).

Pelvis ( Fig. 8A–C ). Characterized by having (1) Os ischium with posterior portion short, tapering rapidly to an angular end (long, tapering gradually to a narrow point in Bubo and Strix ); (2) parapophyses of lumbar and sacral vertebrae robust structures, in ventral view (parapophyses lightly built in Bubo and Strix ).

Femur ( Fig. 8F–I ). Characterized by having (1) Crista trochanteris merging smoothly with shaft anterodistally, in lateral view (similar in Strix ; Crista trochanteris merges abruptly with shaft in Bubo because its distal end is undercut); (2) attachment of M. iliotrochantericus posterior long, narrow, and located near centre of lateral side of proximal end (attachment shorter, broader, and located near posterior edge of lateral side of bone in Strix ; longer, narrow, and centrally positioned on side of bone in Bubo ); (3) Condylus medialis, in posterior view, with lateral end moderately undercut (condyle with lateral end more distinctly undercut, in posterior view, in Strix and Bubo ); (4) Condylus lateralis, in posterior view, as wide as or wider than Trochlea fibularis (similar in Strix ; condyle narrower than trochlea in Bubo ); (5) proximal attachment for Impressiones ansae m. iliofibularis (biceps loop) centrally located on lateral side of shaft (centrally to anteriorly located in Strix ) ( Howard, 1933); (6) Crista lateralis of Sulcus intercondylaris immediately anterior to Fovea tendineus m. tibialis anterior not projecting distad to distal edge of, or beyond, Condylus lateralis (similar in Strix ; projects distad nearly equal to or slightly beyond Condylus lateralis in Bubo ); (7) Crista lateralis of Trochlea fibularis, in lateral view, well-rounded (Crista lateralis similar to elongated in Bubo ; less rounded, more elongated posteriad in Strix ); (8) Condylus lateralis with axis at a significant angle to long axis of shaft (Condylus lateralis nearly parallel with long axis of shaft in Strix and Bubo ); (9) Fovea fibularis broadly and moderately to deeply excavated into lateral side of Condylus lateralis (Fovea fibularis a small, moderate to deep pit not excavated into side of Condylus lateralis in Bubo and a moderately deep pit with a portion slightly excavated into side of Condylus lateralis in Strix ).

Although Howard (1933) correctly noted that in Bubo virginianus the proximal attachment for Impressiones ansae m. iliofibularis was located near the anterior edge of the shaft, and was useful for distinguishing Oraristrix brea and B. virginianus , this character did not hold up well as a generic character when other species of Bubo were examined.

Tibiotarsus ( Fig. 8L–O ). Characterized by having (1) Crista cnemialis anterior extending only slightly proximad of Crista patellaris (similar in Strix ; extends significantly more proximad in Bubo ); (2) Fac. artic. medialis with medial and posterior edge well rounded, in proximal view (less rounded and projecting much more posteriad in Strix and Bubo ); (3) Crista cnemialis lateralis long and deeply excavated, or concave, on lateral side (lateral cnemial crest similar in length and excavation in Strix ; shorter and less excavated in Bubo ); (4) M. gastrocnemius, pars interna, with distal attachment scar very broad, short, not extending distal to Crista cnemialis anterior (not as broad, longer, extending short distance distal to Crista cnemialis anterior in Strix ; narrow, very long, extending considerable distance distal to Crista cnemialis anterior in Bubo ) ( Howard, 1933); (5) Fac. artic. lateralis broadened laterally, with relatively low profile (i.e., sloping less steeply laterad), in posterior view (narrower, with much higher profile in Strix and Bubo ); (6) Fac. artic. medialis with flattened anterolateral corner and, in posterior view, no notch between it and Fac. artic. lateralis (facet with anterolateral corner projecting prominently proximad in Strix and Bubo , with a notch between Fac. artic. medialis and Fac. artic. lateralis); (7) Sulcus extensorius with distal portion (i.e., just proximal to Incisura intercondylaris) deeply and broadly excavated (sulcus generally deep, but slightly less broadly excavated in Strix ; moderately deep and less broadly excavated in Bubo ).

Howard (1933:68) stated that she found there was less angular difference present in Strix relative to Bubo between lines drawn tangent to the proximal and distal edges of the condyles. With additional species and a larger series of comparative material we found this character too variable and difficult to quantify to be reliable for distinguishing genera.

Fibula ( Fig. 8R ). Characterized by having (1) Caput fibulae without obvious sulcus posterior to lateral tuberosity (sulcus better developed in Strix and very well developed in Bubo ); (2) Caput fibulae deeply excavated anteriorly, with anteromedial corner undercut (deeply, but not as broadly, excavated anteriorly in Strix , with anteromedial corner not undercut; robust anteriorly, only slightly concave and not undercut anteriorly in Bubo ); (3) posterior flange with posteromedial corner rounded, not ending in a pointed protuberance (posteromedial corner ends in a pointed or blunt protuberance in Strix and Bubo ).

Figures

Figure 1. Holotypic tarsometatarsus of Oraristrix brea (LACM RLB E9379) in (A) anterior, (B) lateral, (C) posterior, (D) medial, (E) proximal, and (F) distal views. Lateral view (G) of distal tarsometatarsus of O. brea (LACM RLB K9623) illustrates the straight posterior edge of the lateral condyle of Trochlea III. Scale bar = 20 mm.

Figure 2. Intra-element proportions of the tarsometatarsus of Oraristrix brea distinguish it from modern species of owls. (A) Scatter diagram of length vs. width of posterior surface of hypotarsus. For its length, the posterior surface of the hypotarsus of O. brea is relatively narrow compared to that of modern owls. (B) Scatter diagram of total length vs. minimum shaft width of tarsometatarsus. The length of O. brea is within the upper values for Bubo virginianus, but most of the fossils have a relatively slender shaft. (C) Scatter diagram of total length vs. distal width of tarsometatarsus. The length of O. brea is within the upper values for Bubo virginianus, but most of the fossils have a relatively narrower distal end.

Figure 3. Intra-membral and inter-membral element plots give an indication of how Oraristrix brea differed from the modern owls Bubo bubo, B. virginianus, Strix nebulosa, S. occidentalis, S. varia, and S. aluco. (A) Tarsometatarsus length vs. tibiotarsus length. (B) Femur medial length vs. carpometacarpus length. (C) Tarsometatarsus length vs. humerus length. (D) Tarsometatarsus length vs. coracoid medial length. (E) Tarsometatarsus length vs. Carpometacarpus length. (F) Femur medial length vs. humeral length. For the modern species,… [continued on facing page]

Figure 4. Rostrum maxillare of Oraristrix brea (LACM RLB K2713) in (A) lateral, (B) ventral, and (C) posterior views. Sternum of O. brea (LACM RLB F2477) in (D) anterior, (E) ventral, and (F) lateral view. Scapula, left, of O. brea (LACM RLB H6613), in (G) dorsolateral, (H) dorsomedial, and (I) ventromedial views. Close-up of glenoid facet of (J) O. brea (LACM RLB H6613), (K) Bubo virginianus (LACM 109120), and (L) Strix nebulosa (MVZ 151874) illustrating the consistent differences in the shape of this facet among the species. Coracoid, right, of O. brea (LACM RLB F9687), in (M) ventral, (N) dorsal, and (O) medial view. Sternal ends of (P) B. virginianus (LACM 109120), and (Q) S. nebulosa (MVZ 155426) illustrate the differences in their Angulus medialis. The differing placement of the Linea intermusculare and the size of the Fac. artic. sternalis can also be noted. Clavicula, left, of O. brea (LACM RLB E9233), in (R) lateral view. Scale bar = 20 mm.

Figure 5. Humerus, right, of Oraristrix brea (LACM RLB E9804), in (A) anterior and (B) posterior view, and (C) proximal end in anteroproximal view.Anteroproximal view of proximal ends of (D) Bubo virginianus (LACM 109226), and (E) Strix nebulosa (MVZ 155426) illustrates the differences in the form of the Crista bicipitalis and the Sulcus ligamentum transversus. Radius, left, of O. brea (LACM RLB K9798), in (F) anterior, (G) proximal, and (H) posterior view.Anteroventral view of left proximal radii of (I) O. brea (LACM RLB K9798), (J) S. nebulosa (MVZ 151874), and (K) B. virginianus (LACM 109226) illustrates the differences in the form and position of the attachment for M. biceps brachii. Radius, distal end, left, of O. brea (LACM RLB K9627), in (L) dorsal, (M) distal, and (N) ventral view. Carpometacarpus, left, of O. brea (LACM RLB K9432), in (O) dorsal and (P) ventral view. Scale bar = 20 mm.

Figure 6. Ulna, right, of Oraristrix brea (LACM RLB E9544), in (A) anterior, (B) ventral, and (C) posterior view. Anteroproximal view of (D) O. brea (LACM RLB E9804), (E) Bubo virginianus (LACM 87413), and (F) Strix nebulosa (MVZ 155426) illustrate the differences in form of the olecranon and the position of the Tuberculum lig. coll. ventralis. Scale bar = 20 mm.

Figure 7. A scatter plot of total length vs. distal width of the carpometacarpus of Oraristrix

Figure 8. Synsacrum of Oraristrix brea (F3700) in (A) anterior, (B) ventral, and (C) lateral view. Views of the posterior ischium of (D) Bubo virginianus (LACM 110180) and (E) Strix nebulosa (MVZ 151874) illustrate the differences in the posterior ends of this bone in these species. There is no breakage to the posterior ischium of O. brea. Femur, right, of O. brea (K9427) in (F) anterior, (G) posterior, and (H) lateral view. Lateral views of the left proximal femur of (I) O. brea (K9428), (J) S. nebulosa (MVZ 155426), and (K) B. virginianus (LACM 109226) illustrate the differences in form of the Crista trochantericus and position of the attachment of M. iliotrochantericus posterior.Tibiotarsus,left, of O. brea (E9888) in (L) anterior, (M) posterior, and (N) proximal view. Medial views of left proximal tibiotarsi of (O) O. brea (E9888), (P) B. virginianus (LACM 109226), and (Q) S. nebulosa (MVZ 155426) illustrate the differences in form of the Crista cnemialis anterior and the size and position of the attachment of M. gastrocnemius, pars interna. Fibula, left, of O. brea (H9244) in (R) lateral view. Scale bar = 20 mm.