Bull. Kitakyushu Mus. Nat. Hist. Hum.The Appendicular Hist., Ser. A, 12Anatomy: 1–48, ofMarch the Elegant 31, 2014 Crested Tinamou (Eudromia elegans) 1

The Appendicular Anatomy of the Elegant Crested Tinamou 北九州市立自然史・歴史博物館研究報告A類（自然史）投稿要領 (Eudromia elegans)

1 2 3 4 uzuki hiba an uren hashi １. 分野：自然史に関する原著論文，短報等（和文または欧文）でつぎのうち一つ以上にあたるもの． Daisuke S , Kentaro C , Collin S. V B & Tomoyuki O 1 ⑴ 北九州域の自然史に関するもの． Department of Anatomy, Sapporo Medical University, School of Medicine, Sapporo 060-8556, Japan 2 ⑵ 当館の収集活動に関するもの（例：新種記載に際して，ホロタイプまたはパラタイプ・トポタイ Department of Ecology and Evolutionary Biology, University of Toronto, Toronto M5S 3B2, Canada 3 プ等の標本が当館に収蔵される場合）． Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom. 4 ⑶ 当館の行う調査研究に関係するもの． Kitakyushu Museum of Natural History & Human History, Kitakyushu 805-0071, Japan ⑷ 既に当館に収蔵されている標本に関するもの． (Received December 28, 2012; accepted February 4, 2014) ⑸ 当館学芸員の研究活動に関係するもの． ⑹ 編集委員会が適当と認めるもの． ABSTRACT — Tinamids are small cursorial birds with limited flight ability. They are phylogenetically nested within a clade composed mostly of large, flightless birds (ratites). Their ability to fly and the evolution of flightlessness in the clade are currently not well understood, and this is largely due to a paucity of literature on the ２. 審査：投稿原稿は，編集委員会ならびに委託された査読者による審査の後採否が決定される．修正 osteological and muscular anatomy of these birds. の必要のあるとされた原稿は，査読者の意見と共に返送されるので，著者は必要な訂正を行った後， Two Eudromia elegans (Palaeognathae: Tinamidae) were dissected and four skeletons were examined. The 速やかに再提出する．体裁については編集委員会に一任される． skeletons of Eudromia are characterized by a thin sternum, short and stout humeri, and developed lower limbs. Eudromia maintains some ancestral characters in the postcranial skeleton, such as elongated lateral trabeculae of the sternum, an absent rostral external spine of the sternum, and lack of fusion between the distal ilium and ３. 北九州市立自然史・歴史博物館研究報告Ａ類（自然史）に掲載された論文の著作権（著作財産権， ischium. The lost of the hallux suggests cursorial adaptation occured not only in Strutioformes (Struthio has only Copyright）は，北九州市立自然史・歴史博物館に帰属するものとする． two digits) but also even in tinamids. Accordingly, the muscles inserting on the hallux are lost or shifted to other digits. However, the body plan of Eudromia is quite similar to other modern volant birds, like Gallus. Our specimens showed differences in musclular morphology from previous descriptions of tinamou anatomy, ４. 投稿を希望される方は，あらかじめ下記にご連絡下さい． particularly, the absence of M. iliofemoralis internus and the femoral head of M. tibialis cranialis. We also compared Eudromia with other ratites, such as Struthio, Rhea, Apteryx, and Dromaius. In the shoulder girdle, Eudromia has a large M. pectoralis thoracica and M. supracoracoideus, which are used for the downstroke and upstroke, 連絡先：北九州市立自然史・歴史博物館 respectively, but these muscles do not have such antagonistic actions in other ratites due to differing origins and 〒 ８０５－００７１ insertions. The morphological changes in the pelvic girdle are minor compared with those in shoulder and forelimb 北九州市八幡東区東田二丁目４番１号 regions. Ratite have enlarged Mm. femorotibiales, and M. iliotorochantericus medius and M. ischiofemoralis are diminished in size, except in . has a thin M. caudofemoralis pars pelvica, while other ratites have 電話 （０ ９３）６８１－１０１１ Apteryx Eudromia lost M. caudofemoralis pars caudalis (in Dromaius and Rhea) or it is considerably diminished (in Struthio). The ＦＡＸ （０９３）６６１－７５０３ differences between Eudromia and other ratites we find are attributed to the retention of flight ability in Eudromia.

KEY WORDS: Tinamou, Osteology, Myology, Comparative anatomy

INTRODUCTION to all other palaeognaths (e.g., Cracraft, 1974; Caspers et al., 1994; Cracraft & Clarke, 2001) and others recovering Tinamous (Palaeognathae: Tinamidae) are a monophyletic the ostrich (Struthio) as the outgroup to all other palaeognaths group of small, primarily cursorial birds capable of short bursts (Harshman et al., 2008; Phillips et al., 2010; Johnston, 2011; of flight when necessary. Because tinamous are nested within Haddrath & Baker, 2012). the clade Paleognathae which is composed of all flightless Some authors have been suggested the flight ability was birds except for tinamous, there is a debate about whether flight lost multiple times in Palaeognathae, which is used to explain in this family is due to retention of the ancestral condition, the clade’s global distribution (Harshman et al., 2008; Phillips or if they re-evolved the ability to fly (e.g., Harshman et al., et al., 2010). However, parsimony-based character analysis 2008; Phillips et al., 2010). This debate is in part due to the suspended this conclusion because there was lack of evidence ambiguity surrounding their phylogenetic relationships to other to suggest homology in the pectoral characters (Livezey & Zusi, palaeognaths, with some analyses considering them the outgroup 2007). 2 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Despite numerous morphological phylogenies of Table 1. Examined specimen (skeletons). palaeognaths, little work has been done to document the Institute No. Genus Specis udson ( ) morphology of tinamous. H et al. 1972 described the NMNS A343 Eudromia elegans myology of 22 specimens of 13 species of tinamous, but they NMNS A344 Eudromia elegans did not describe osteological morphology. Many morphological YIO 00321 Eudromia elegans phylogenies use a limited character matrix of <100 characters YIO 00325 Eudromia elegans (Cracraft, 1974; Johnston, 2011) and are the only phylogenies YIO 60631 Nothoprocta cinerascens which are able to incorporate fossil taxa that may aid in testing hypotheses of multiple losses of flight. The goal of the present study is therefore to describe the myology and osteology of the Elegant Crested Tinamou (Eudromia elegans) as a tool for future DESCRIPTION work on the phylogeny of extinct and extant palaeognaths. By comparing the anatomy of E. elegans to other extant archosaurs Osteology (both crocodylians and birds), we also highlight similarities and differences in the anatomy that might help future studies begin 1. Scapula (Figures 1, 4) to explore the question of multiple losses of flight or a single gain of flight in palaeognaths from an anatomical perspective. The scapula consists of thick proximal portion composed of the glenoid and acromion processes and an elongated scapular Institutional Abbreviation – KMNH: Kitakyushu blade. The coracoid tubercle, where the coracoid articulates with Museum of Natural History and Human History, Fukuoka, the scapula, is located between the glenoid and the acromion. Japan; YIO: Yamashina Institute of Ornithology, Chiba, Japan. The clavicular facet, which is the articular facet for the furcula, is located distal to the acromion. The glenoid process of the scapula contributes to the glenoid fossa along with the glenoid MATERIALS AND METHODS process of the coracoid, which articulates with the humerus. The scapulo-coracoid joint of is not as large as in Two elegant crested tinamous (Eudromia elegans) (KMNH Eudromia VR 700,000 and YIO 2006-0047) were used. These specimens crocodiles and non-avian dinosaurs, whose joints are tightly are stored in the Kitakyushu Museum of Natural History and connected or sometimes fused. Human History, Kitakyushu City, and Yamashina Institute of The dorsoventral width of the scapular blade is relatively Ornithology, Abiko, Japan. KMNH VR specimen was three years consistent along the proximodistal length of the scapula, and one month old at the time of death, 45 cm in total length and the mediolateral thickness reduces distally. The dorsal (from the nib to the tip of the rectrix), and 695 g in weight. The margin is occupied by the insertion of M. rhomboideus cause of death was systemic amyloidosis. YIO specimen was superficialis laterally and M. rhomboideus profundus medially. one year old at the time of death, total length could not measured The lateral surface of the scapular blade is smooth and lacks (cranial part was removed, but the size was almost same as rugose osteological correlates. Two tendinous origins of M. KMNH VR specimen), and it was 620 g in weight. scapulotriceps attach proximally on the scapular blade. The These specimens did not have any evident morphological muscular origins of M. subscapularis caput laterale and M. abnormarities, and were frozen and stored at ˗20 °C. KMNH scapulohumeralis caudalis cover almost the entire lateral surface VR 700,000 was then thawed before being fixed in 10 % neutral of the distal scapular blade. formalin. YIO 2006-0047 was not fixed after being thawed. The The medial surface of the scapula is proximally occupied visceral organs of KMNH VR 700,000 had been removed during by the origin of M. subscapularis caput mediale. M. serratus autopsy. Significant damage to the left shoulder girdle occurred superficialis cranialis inserts near the proximal end and the during the autopsy at the zoo prior to our dissection. In addition, insertion is oblique relative to the long axis of the scapular blade, we observed five osteological specimens, stored at the National extending cranially from the ventral margin to the dorsal margin. Museum of Nature and Science, and Yamashina Institute of The insertions of both M. serratus superficialis caudalis and M. Ornithology (Table 1). serratus profundus are located on the distal portion. Because the insertions of Mm. serratus are fleshy, there is no obvious The muscles are identified with comparison to Hudson et osteological correlate for these muscle insertions. al. (1972) and then described based our specimen. The lines of muscle action are estimated from the direction of muscle fibers, tendon and origin an insertion, and confirmed using passive 2. Coracoid (Figures 2, 4) action in postmortem specimens. Osteological and myological The coracoid is generally a major component of the terminology followed Baumel (1993). shoulder girdle in birds and reptiles. The coracoid is articulated The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 3

Fig. 1. The left scaoula of Eudromia elegans with muscle attachment sites. (A) Lateral view. (B) Medial view.

with the furcula and scapula distally and the sternum proximally. also extend onto the glenohumeral joint capsule so that the The coracoid has roughly an hourglass shape with a wider actual size of the origin of these muscles extends beyond the proximal end. The proximal and distal ends are orthogonal to bony surfaces. The articular surface for the furcula is medial to one another, and the coracoid is distally enlarged dorsoventrally the acrocoracoid process, but its surface is small and difficult and enlarged proximally mediolaterally. to distinguish. There is no supracoracoidal foramen as found The articular surface for the scapula is reduced and in non-avian dinosaurs and crocodiles. The ventral side of the shifted caudally compared to the condition in other sauropsids glenoid has a common tendinous origin for Mm. biceps brachii (Vickaryous & Hall, 2006). The coracoid consists of the and coracobrachialis cranialis. The lateral process provides glenoid process that, along with the glenoid process of the the origin for M. coracobrachialis caudalis cranially and the scapula (see above), forms the glenoid fossa, which articulates insertion for M. sternocoracoideus caudally. with the humerus. The glenoid fossa is directed more caudally than in crocodiles, as stated by Bakker (1971). 3. Furcula (Figures 2, 4) The cranial-most portion of the distal end is occupied by the acrocoracoid process (the facet for articulation with the The avian furcula is homologous to fused clavicles in furcula), which comprises the distal border of the triosseal canal. other reptiles. In many reptiles, the clavicles are reduced, but a The distal end of the acrocoracoidal process provides the small robust furcula is maintained in most birds, as it plays a critical fibrous attachment of the furcula and the site of origination for role in avian flight. The fusion of the clavicles occurred in basal both Mm. deltoideus minor and major; however their origins theropod dinosaurs (Norell et al., 1997), and Carrano et al. 4 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 2. The left coracoid and furcula of E. elegans with muscle attachment sites. (A) Coracoid, posterior view. The dotted part of M. subcoracoideus is not for attachment of the coracoid, but the muscle is pass through there. (B) Coracoid, anterior view. (C) Coracoid, dorsal view. (D) Furcula. Ventral and dorsal view The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 5

Fig. 3. The sternum of E. elegans with muscle attachment sites. (A) Lateral view. (B) Dorsal and ventral view.

(2005) suggested the Jurassic coelosauroid Segisaurus had a the clavicular facet, and is connected to the medial side of the furcula, which had previously been regarded as the clavicle. coracoid and the sternum via membrana sternocoracoclavicularis. The furcula of Eudromia is more U-shaped than V-shaped, The cranial margin of the furcula provides the insertion for M. and is very thin. The furcula articulates with the coracoid at pectoralis thoracica. M. deltoideus minor and M. deltoideus pars 6 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 4. The skeleton of the sternal region of E. elegans. (A) Lateral view. Left coracoid and scapula was removed. (B) Ventral view. (C) Medial view.

propatagialis insert on the dorsal cranial surface of the furcula facet, lies between the rostrum sterni and the craniolateral near the dorsal apex, and M. rhomboideus superficialis inserts on tubercle. the dorsal caudal surface. The origin of M. supracoracoideus extends from the sternal carina to the base of the sternal body. The bony origin 4. Sternum (Figures 3, 4) of M. pectoralis is limited to the distal sternal carina. M. pectoralis continues a fleshy origination along the surface In many reptiles, the sternum is highly reduced, and is still of M. supracoracoideus and the sternal notch membrane. M. unossified in Archaeopteryx (Wellnhofer & Tischlinger, 2004). coracobrachialis caudalis originates on the ventral surface of However, modern birds have huge sterna and a sternal carina the craniolateral trabecula. M. subcoracoideus originates on the (keel) protruding from the midline of the sternal body (Baumel dorsal cranial surface of the rostrum sterni. M. sternocoracoideus et al., 1993). This projection is expanded to increase the origin and M. sternocostalis originate on the cranial and caudal portions area for M. pectoralis thoracica and M. supracoracoideus. of the dorsal craniolateral trabecula, respectively. Flightless paleognaths, such as rheas and ostriches, therefore, do not develop the sternal carina at all. On the other hand, tinamids have a developed sternal carina because they have limited flight capabilities and fairly large pectoralis musculature. 5. Humerus (Figure 5) The body of the sternum is mediolaterally thin. The craniolateral trabecula extends laterally from the base of the The humerus is the proximal-most forelimb bone and is sternal body. The intermediate tubercula branches from the expanded at its proximal and distal epiphyses. The deltopectoral sternal body cranially and extends caudally parallel to the sternal crest is developed along the dorsal margin of the proximal body. The sternal notch membrane spans the area between the humerus and is directed cranially, while the dorsal tubercle is body of the sternum and intermediate tubercula. developed on the caudal surface of the proximal humerus. There are costal facets for the articulation of the ribs with The humeral head is oval in proximal view, articulating the sternum on the dorsoproximal intermediate trabecula. The with the glenoid fossa, which is composed of the scapula and rostrum sterni extendeds cranially from the sternal body and is coracoid. Distally, the humerus has two condyles that articulate bifurcated. The articular surface for the coracoid, the coracoidal with the radius and ulna, termed the dorsal (lateral) condyle and The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 7

Fig. 5. The left humerus of E. elegans with muscle attachment sites. (A) Anterior view. (B) Dorsal view. (C) Ventral view. (D) Posterior view. 8 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 6. The left ulna and radius of E. elegans with muscle attachment sites. (A) Dorsal view of ulna and radius. (B) Ventral view.

the ventral (medial) condyle, respectively. The lateral surface Proximally, M. deltoideus minor, the developed tendon of M. of the dorsal condyle is termed the dorsal epicondyle, and the supracoracoideus, and two slips of M. deltoideus major insert medial surface of the ventral condyle is termed the ventral along to the dorsal caudal side of the humerus, in proximodistal epicondyle. order. The insertion of the scapulohumeral ligament is on the Many important flight muscles that cause movement dorsal tubercle, just distal to the humeral head on the caudal at the glenohumeral joint insert onto the proximal humerus. surface of the humerus. The common tendon of M. subscapularis The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 9

Fig. 7. The left manus of E. elegans with muscle attachment sites. (A) Dorsal view. (B) Ventral view.

and M. subcoracoideus and the tendon of M. scapulohumeralis are nearly indistinguishable arranged proximolaterally as M. caudalis insert onto the ventrocaudal surface of the humerus, supinator, M. extensor metacarpi radialis, M. extensor digitorum forming the ventral tubercle. M. scapulohumeralis cranialis communis, and M. ectoepiconylo-ulnaris. inserts proximal to the origin of M. humerotriceps. On the ventral (medial) epicondyle are the origins of the The deltopectoral crest, which is 1/5 the total length of the forearm flexor muscles. These muscle origins are arranged humerus distal from the proximal end, is strongly developed. It proximodistally as M. pronator superficialis, M. pronator provides the insertion of the large M. pectoralis thoracis on its profundus, M. epicondyloulnaris, and M. flexor carpi ulnaris. ventral surface, and the insertion of M. coracobrachialis cranialis The origin of M. flexor carpi ulnaris is separated distally from lies ventrodistal to the insertion of M. pectoralis thoracica. the other flexor origins, but the origins of other forearm flexors The origin of M. humerotriceps spans nearly all of the are nearly indistinguishable from one another. In both flexor and caudal diaphysis. The caudal surface of the diaphysis has a extensor muscle groups, therefore, it is impossible to identify the narrow ridge (caudal margin) and it provides the insertion for M. individual originations based on osteological correlates alone. latissimus dorsi cranialis. M. brachialis originates on the cranial side of the distal diaphysis proximal to the ventral condyle. 6. Ulna (Figure 6) The distal end of the humerus is dorsoventrally expanded. The forearm extensor muscle group originates on the dorsal The forearm consists of the radius and ulna. The ulna is (lateral) epicondyle. The forearm extensor muscle origins longer and thicker than the radius. A slight olecranon process 10 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 8. The pelvis of E. elegans with muscle attachment sites. (A) Lateral view. (B) Medial view. (C) Dorsal view. The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 11

Fig. 9. The pelvic girdle of E. elegans. (A) Dorsal view. (B) Ventral view.

is developed on the proximal ulna and provides the common flexor digitorum profundus originates distally to M. brachialis insertion site for M. scapulotriceps and M. humerotriceps. The and M. entepicondyloulnaris along the majority of the diaphysis. ulnar head articulates with the entire ventral condyle and a M. ulnometacarpalis ventralis originates on the distal diaphysis part of the dorsal condyle of the humerus. The boundary of the near the epiphysis. articulation of the two condyles is separated by the intercondylar crest on the ulnar head. Distally the ulna articulates with the 7. Radius (Figure 6) ulnare. The origin of M. extensor digitorum communis lies on the The radius is a rod-like bone that is not expanded at either proximodorsal surface. The proximodorsal ulna is the insertion epiphysis, instead maintaining a relatively consistent width area for many of the extensor muscles. M. ectoepicondylo- along its length. The radial head articulates with a portion of the ulnaris inserts onto the caudal part of the diaphysis and the dorsal condyle of the humerus proximally and with the ulnar papillae of the remiges, which are traces of the flight feathers head caudally, making the radioulnar joint. Distally the radius along the caudal margin. The cranial part of the proximal ulnar articulates with the radiale of the carpus. diaphysis has the origin of M. extensor pollicis longus. The M. biceps brachialis inserts onto the ventral surface of joint origin of M. ulnometacarpalis dorsalis lies on the distal dorsal capsule of the radioulnar joint and the proximoventral surfaces surface of the ulna near the epiphysis. of the radius and ulna, leaving obvious scars on these bones. The flexor muscles attach to the ventral surface of the ulnar M. supinator inserts onto the proximodorsal radial diaphysis. diaphysis. M. brachialis and M. entepicondyloulnaris insert onto M. extensor pollicis longus originates on the dorsal midshaft a ridge that extends distally from the intercondylar crest. M. of the radius, and M. extensor indicis longus originates on the 12 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

posterodistal diaphysis. The ventral diaphysis serves as the et al., 2001). The carpometacarpus-phalanx I1 joint, therefore, insertion site for M. pronator profundus proximally and M. is the only MP joint have a large range of motion not only pronator superficialis distally. with adduction/abduction, but also with flexion/extension and internal/external rotation. It also provides the area of insertion 8. Proximal carpus (Figure 7) for muscles that control these movements. The second digit has

two phalanges—the proximal phalanx (II1) and distal phalanx

The proximal carpus of Eudromia consists of the ulnare (II2). Both phalanges have the flanges on their lateral surfaces. and radiale. The radiale is wedge-shaped and firmly articulated The third digit has one small phalanx (III1). with the radius. There is no mobility at the radius-radiale- carpometacarpus joints. This articulation artificially elongates 11. Ilium (Figures 8, 9) the radius to make it longer than the ulna. As a result, the wrist is naturally in an ulnarly flexed position. The avian pubis, ischium, and ilium are fused firmly each The ulnare is not located directly between the ulna and other and have obliterated sutures. The dorsal portion of the carpometacarpus, and is instead located on the ventral surface of acetabulum, which articulates with the head of the femur, is the carpometacarpus. The bone limits palmar flexion and overall derived from the ilium, the cranial ventral portion is formed range of motion at the wrist joint. The tendon of M. flexor carpi by pubis, and the caudal ventral portion is formed by ischium. ulnaris and M. flexor digitorum superficialis insert on the ventral When articulated, the acetabulum completely covers the femoral surface of the ulnare. head with the developed acetabular roof (the dorsal rim of the acetabulum); there are no thick menisci as in crocodiles 9. Carpometacarpus (Figure 7) (Suzuki et al., 2011). Caudal to the acetabulum is the developed antitrochanter, which receives the femoral facies articularis It has been debated whether the avian wing contains digits antitrochanterica. II-III-IV with a reduced digit I and V (Burke & Feduccia, 1997; Another unique character of the avian pelvis is the lack Xu et al., 2009) or digits I-II-III with digits IV and V reduced of an articulation between the left and right ischia and pubes; (Padian & Chiappe, 1998; Vargas & Fallon, 2005). This paper the pelvic floor is supported solely by trunk muscles. The followed the latter according to Tamura et al. (2011). iliac blade is elongate craniocaudally and separated by the The carpometacarpus is composed of the fused metacarpals relative placement of the acetabulum. The cranial expansion (I-III) and distal carpals. The pisiform process, which is is the preacetabular process, and the caudal expansion is the a remnant of the pisiform, is projected ventrally from the postacetabular process. M. iliotibialis cranialis originates ventral surface of the proximal carpometacarpus. The alular cranially on the preacetabular process, and M. iliotibialis process is the remnant of metacarpal I, which is very short lateralis originates on the caudal preacetabular process. and slightly protrudes to make the articular surface of the The lateral surface of the preacetabular process is concave, first phalanx of the first digit (I1), the metacarpophalangeal and it is largely occupied by the origin of M. iliotrochantericus joint. The second metacarpal is the most robust and longest in caudalis. The ventral margin is occupied by the origins of the carpometacarpus. The ventral surface of the diaphysis of Mm. iliotrochantericus cranialis and medialis. M. iliofemoralis metacarpal II has a fleshy insertion point for M. adductor indicis. externus originates dorsal to the acetabulum, around the The third metacarpal is thin, but almost as long as the metacarpal undefined barrier of the pre- and post-acetabular processes. The II. The diaphysis is strongly bowed, creating a space between lateral surface of the postacetabular process provides the origin metacarpals II and III. The edge of this space is the insertion of M. iliofibularis and the ventral margin provides the origin area for M. interosseous ventralis ventrally and M. interosseus of M. caudofemoralis pars pelvica. The dorsal surface of the dorsalis dorsally. postacetabular process is expanded, but no muscles attach here.

12. Pubis (Figures 8, 9) 10. Manual Phalanges (Figure 7) In birds, the pubis is very small compared to other pelvic The digits generally have limited capacity for flexion and elements. The pubis comprises the anteroventral portion of the extension at the metacarpophalangeal (MP) and interphalangeal pelvis in most reptiles, but the pubis of birds is rotated caudally, (IP) joints. Each phalanx is flat and thin, and the articular and is parallel to the ischium. surface is expanded craniocaudally to allow adduction and The pubis has a small cranial projection, called the abduction. The proximal phalanx of the first digit (I1) is the prepubic process. M. ambiens originates on the prepubic largest and longest of all the phalanges. It forms the alula, process. The area ventral to the acetabulum at the boundary of which is important for maintaining lift during landing (Alvarez the pubis and ischium is the origination site of M. obturatorius The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 13

Fig. 10. The left femur of E. elegans with muscle attachment sites. (A) Medial view. (B) Anterior view. (C) Lateral view. D. Posterior view.

lateralis. The puboischiadic membrane spans both the pubis and site for M. obturatorius medialis. This insertion continues onto ischium, and the membrane provides the origin area for Mm. the ilioischiadic and puboischiadic membranes. The lateral puboischiofemoralis pars medialis (anteroventral) and lateralis surface of the ischium is almost completely occupied by the (posteroventral) and M. flexor cruris medialis( dorsal). origin of M. ischiofemoralis.

13. Ischium (Figures 8, 9) 14. Femur (Figure 10)

The ischium constitutes the caudal portion of the pelvis. The femur is the proximal-most long bone of the hind It is more robust than the pubis. Two membranes attach to the limb. The femoral head, which articulates with the acetabulum, ischium, connecting it to the other elements of the pelvis. The is spherical (unlike the condition seen in other reptiles) and ilioischiadic membrane spans the caudal distance between the clearly distinguished from the shaft by the femoral neck. The ilium and ischium, and the puboischiadic membrane spans the trochanteric crest is expanded farther cranially and dorsally and space between the ischium and pubis. is higher than the femoral head, whereas other palaeognaths The cranial edge of the proximal ischium projects the have a reduced femoral trochanter. The cranial margin of the obturator process, which creates the obturator notch with the femoral trochanter extends distally to the middle of diaphysis caudal margin of the pubis. Obturator nerves, arteries, and veins to create the trochanteric crest. The diaphysis is almost straight pass through the obturator foramen, innervating and circulating with a slightly caudal curve distally. the “adductor” region. The distal epiphysis is comprised of the medial and lateral The medial surface of the ischium has a large origination epiphyses, with the lateral epiphysis being slight larger. The 14 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 11. The left crus of E. elegans with muscle attachment sites. (A) Anterior view. (B) Medial view. (C) Posterior view. (D) Lateral view. E. Anterolateral view of juvenil E. elegans. The cranial cnemial crest and the patella or neomorph are unfused.

lateral surface of the lateral condyle has an indentation, which is dividing the origin of M. femorotibialis lateralis and M. the articular surface for the fibular head. The intercondylar fossa femorotibialis intermedius. The caudal surface contains the linea separates the two condyles and allows the cranial and caudal intermuscularis caudalis that extends along the diaphysis to cruciate ligaments to pass between them. the medial epicondyle along the boundary between the origins A number of muscles attach to the femur, some of which of Mm. femorotibialis medialis and externus. All insertions have tendinous insertions and cause discernable muscle scarring. are fleshy, excluding the caudal margin of M. femorotibialis The proximal trochanteric crest is the insertion site of M. medialis, which has an aponeurotic origin along linea iliotrochantericus caudalis, and Mm. iliotrochantericus cranialis intermuscularis caudalis, so there are few obvious traces of and medius insert ventrally (distally) to M. iliotrochantericus muscle insertion. caudalis. The lateral surface of the femoral trochanter has the The caudal surface of the distal diaphysis contains many strong tendinous insertion of M. obturatorius medialis and muscle insertions. M. flexor cruris lateralis pars accessorius weak fleshy insertion of M. obturatorius lateralis. Ventral to the inserts along the ridge that extends from the medial condyle. insertions of Mm. obturatorius, there are tendinous insertions Lateral to this ridge, there are the fleshy insertion of M. of M. iliofemoralis externus and M. ischiofemoralis. These two puboischiofemoralis and the fleshy origin of the intermediate insertions are almost the same size, and both create impressive head of M. gastrocnemius. Near the intercondylar fossa, there scarring. is a common origin of the medial head of M. flexor perforans The diaphysis is mostly covered by the origins of Mm. digiti (FP) IV, FP III, FP II, M. flexor hallucis longus (FHL), and femorotibiales. The cranial surface of the diaphysis contains M. flexor digitorum longus (FDL) from proximal to distal. This the linea intermuscularis cranialis that extends along the area on the femur has a rugose surface, but it is not possible to diaphysis from the trochanteric crest to the medial epicondyle, distinguish individual muscle insertions. The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 15

Fig. 12. The left pes of E. elegans with muscle attachment sites. (A) Dorsal view. (B) Plantar view. The inset shows the terminology of each bone of the pes.

The lateral epicondyle provides the origins of the lateral 15. Tibiotarsus (Figure 11) head of M. gastrocnemius, M. flexor perforans et perforatus digiti (FPP) II, FPP III and the lateral head of FP IV from The tibiotarsus is longer than the femur, and the diaphysis proximal to distolateral. Ansa iliofibularis attaches proximal to is almost straight. The proximal epiphysis is the strongly these muscles. In addition, the lateral collateral ligament (LCL) expanded tibiotarsal plateau, the articular surface for the attaches on the lateral epicondyle, cranial to FPP III; the lateral condyles of the femur via thick menisci (Herzmark, 1938), and epicondyle has rough surface overall. the large cnemial crests. The plateau is divided into the medial The medial epicondyle has only the insertion of the medial and lateral facet and between the facets, there is a slightly collateral ligament (MCL). This attachment site is slightly uplifted intercondylar eminence for the insertion of the anterior concave, but the epicondyle is mostly smooth. cruciate ligament (ACL). The distal epiphysis of the tibiotarsus forms a trochlea, differing from the reptilian tibia, which forms 16 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi an astragular facet. The tibiotarsus of birds is the bone composed 17. Tarsometatarsus (Figure 12) of the fused tibia, astragalus, and calcaneum (e.g., McGowan, 1984, 1985), shown by the incomplete fusion of these elements The tarsometatarsus is rod-like and approximately two- in closely related alverezsaurid theropods (Chiappe et al., thirds the length of the tibiotarsus. It is comprised of fused 2002). The tibiotarsal trochlear surface articulates with the metatarsals II-IV. The first metatarsal of most tinamids is not tarsometatarsus, forming hinge joint. fused to metatarsals II-IV, and instead attaches to the midshaft In birds, the most prominent features on the proximal of the tarsometatarsus. However, the first metatarsal is lost in tibiotarsus are the enlarged cranial and lateral cnemial crests, Eudromia. The distal end is tri-radiate, forming the articular located cranial and somewhat medial to the tibiotarsal plateau. surfaces for the proximal phalanges. The avian embryo also The cranial cnemial crest is considered to correspond to a develops separated metatarsals that fuse ontogenetically. neomorphic tibial tuberosity (Fig. 11E; Barnett & Lewis, 1958; There are proximally two cotyles that articulate with the Vickaryous & Olson, 2007; Hutchinson pers. comm.) while distal trochlear surface of the tibiotarsus, which are separated dinosaurs have only one cnemial crest, corresponding to the by a central eminence. The proximodorsal eminence is reduced lateral cnemial crest of birds (Hutchinson, 2002). for the origin of M. extensor proprius digiti III. M. tibialis The dorsal surface of the cranial cnemial crest contains cranialis inserts distal to the origin of M. extensor proprius digiti the common insertion of Mm. iliotibialis cranialis and lateralis III, leaving two oval scars. On the proximal ventral surface, and Mm. femorotibialis medialis and lateralis. The lateral there is a bony tuberosity called the hypotarsus that covers the surface contains the origin of M. fibularis (peroneus) longus, tibial cartilage. The hypotarsus is the insertion for each tendon and the medial surface contains the origin of the medial head of M. plantalis and M. gastrocnemius (Achilles tendon). The of M. gastrocnemius. M. fibularis longus and the medial head hypotarsus has grooves through which tendons of FHL, FPP of M. gastrocnemius are developed significantly in birds. The II, FP II, III and IV, and FDL pass, thus stabilizing the tendons. origin of M. tibialis cranialis extends over the lateral cnemial Different from the condition seen in Gallus, all tendon pathways crest and proximal fibula. The medial proximal surface of are grooved, but do not become canals. the tibiotarsuscontains the insertion of the MCL and a weak The diaphysis is fairly straight. M. abductor digiti II, insertion of M. flexor cruris lateralis directly caudal to the MCL. M. extensor brevis digiti III, and M. extensor brevis digiti IV M. popliteus and M. plantaris insert ventral to the caudal margin originate dorsally on the tarsometatarsus in mediolateral order. of the medial facet. Between the medial and lateral facet, there The ventral surface contains the sulcus tendinis to direct the is a shallow fossa, which is the insertion of M. flexor cruris flexor tendons. M. abductor digit IV also originates laterally on lateralis pars pelvica. the ventral surface, and M. adductor digiti II arise distally on the The tibiotarsal diaphysis is straight and has a consistent ventral surface. diameter over most of its length. M. flexor digitorum longus originates on the cranial surface of the diaphysis. The medial 18. Pedal phalanges (Figure 12) head of M. gastrocnemius originates on the medial diaphysis, and M. extensor digitorum longus originates on the caudal Eudromia has three pedal digits (II-IV). The digits II, III, diaphysis. The lateral proximal surface of the tibiotarsus and IV have three, four and five phalanges, respectively (digital develops the fibular crest, which articulates with the proximal formula = x:3:4:5:x). The proximal phalanx is the longest. diaphysis of the fibula. The distal-most diaphysis has two tendon Although all the phalanges are similar in morphology, the canals, formed by the ossification of the pons supratendinous, phalanges of the second and third digits are relatively large, but which separates the paths of the EDL tendon. There is almost no small in digit IV. The distal phalanx of each digit forms a claw. muscle attachment on the distal tibiotarsus. Myology 16. Fibula (Figure 11) Muscles in the Forelimb The fibula is very thin, tapering distally until becoming a connective tissue that fuses to the diaphysis of the tibiotarsus. 1. Muscles from the trunk and shoulder girdle, However, the fibular head is relatively large and articulates with Dorsal group the lateral condyle of the femur. The proximal fibula contains the origin of M. tibialis cranialis cranially and the LCL laterally. The M. rhomboideus (Figure 13) caudal surface contains the origin of FP II and the insertion of M. M. rhomboideus is divided into M. rhomboideus popliteus. M. iliofiburalis inserts laterally, and FP IV originates superficialis and M. rhomboideus profundus. These are well on the anteromedial mid-diaphysis. developed and are deep to M. latissimus dorsi cranialis. These muscles adduct the scapula. The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 17

Fig. 13. The Dorsal and shoulder musculature of E. elegans. (A) Dorsal superficial musculature. (B) Superficial musculature of the lateral aspect of the scapula. (C) Musculatures of the medial aspect of the scapula.

M. rhomboideus superficialis M. serratus (Figure 13) M. rhomboideus superficialis originates from the spinal M. serratus extends from the ribs to the scapula and processes of the first to fifth thoracic vertebrae aponeurotically. stabilizes the scapula on the trunk. It is usually divided into The muscle runs anterolaterally and has a fleshy insertion onto M. serratus superficialis and M. serratus profundus, and the the dorsal margin of the scapula. former is further divided to Mm. serratus superficialis cranialis, caudalis, and metapatagialis in most birds, including Eudromia. M. rhomboideus profundus Unlike Mm. rhomboideus, Mm. serratus superficialis and M. rhomboideus profundus also has a fleshy origin on the profundus do not overlap each other, and the insertions are well spinal processes of the first to fifth thoracic vertebra. This muscle separated. runs posterolaterally, and the direction is almost orthogonal to M. rhomboideus superficialis. This muscle is thicker and larger M. serratus superficialis cranialis than M. rhomboideus superficialis. The aponeurotic insertion of M. serratus superficialis cranialis has a fleshy origin on the M. rhomboideus profundus is on the medial surface of the dorsal uncinate process of the first and second thoracic ribs. uH dson et margin of the scapular blade. al. (1972) described the origin on the last two cervical ribs. The muscle belly is thin and narrow, running anterodorsally, inserting 18 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 14. Musculature of the pectoral region of E. elegans. (A) Ventral view. All muscles are removed on the right side. (B) Lateral view of left pectoral region. M. pectoralis pars thoracica and muscles in scapular region are removed. (C) Ventral view. Superficial musuluture of the pectoral region.

onto the proximal medial surface of the scapular blade. the three muscle slips runs posterodorsally, deep to M. serratus superficialis cranialis. The muscle slips merge into one slip M. serratus superficialis caudalis and have a fleshy insertion on the medial surface of the dorsal M. serratus superficialis caudalis originates on the uncinate margin of the scapular blade. processes of the first to forth thoracic ribs. The muscle belly is larger than that of M. serratus superficialis cranialis. The muscle 2. Muscle from trunk to the shoulder girdle, Ventral runs posterodorsally and inserts onto the medial surface of group distal-most scapular blade. M. sternocoracoideus M. serratus superficialis metapatagialis M. sternocoracoideus has a fleshy origin on the cranial M. serratus superficialis metapatagialis has a fleshy origin dorsal margin of the sternum, on the craniolateral trabecula. It on the third thoracic rib and is a long, narrow muscle. The distal is a short, but powerful muscle and makes up the cranial wall of part was damaged in our specimen, and we cannot confirm thorax. The fleshy insertion is on the posterolateral surface of the the insertion. Hudson et al. (1972) described it as running proximal coracoid. anterodorsally, inserting near the caudal end of the humeral tract, i.e. near the axilla. 3. Muscles from shoulder girdle/trunk to humerus, Dorsal group M. serratus profundus M. serratus profundus originates on the transverse M. latissimus dorsi (Figure 13) processes of the three posterior-most cervical vertebrae. Each of M. latissimus dorsi is divided into three parts, Mm. The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 19

Fig. 15. Musculature of the brachial region of E. elegans. (A) Superficial musculature of the humerus, anterior view. (B) Deep musculature of the humerus, anterior view. M. pectoralis pars thoracica and M. biceps brachii are removed. (C) Superficial musculature of the humerus, posterior view. (D) Deep musculature of the humerus, posterior view. M. scapulotriceps is removed.

latissimus dorsi cranialis, caudalis, and metapatagialis. These M. serratus superficialis caudalis and superficial to M. serratus muscles comprise the most superficial layer of the dorsal region, superficialis metapatagialis. The muscle is tapered suddenly near as in other reptiles, but this muscle is not as divided in most insertion and becomes aponeurotic. It inserts onto the skin and other reptiles. This group forms the caudal part of the axillary the fascia of M. latissimus dorsi cranialis, M. deltoideus major, wall and inserts onto the humerus and axilla. This muscle and M. scapulotriceps. retracts the humerus at the glenohumeral joint. M. latissimus dorsi metapatagialis M. latissimus dorsi cranialis This muscle was also damaged, so the morphology and M. latissimus dorsi cranialis originates on the spinal origin could not be clearly confirmed. It originates on the spinal processes of thoracic vertebrae II-VI. It runs anterolaterally processes of the posterior thoracic vertebrae and is very thin and superficial to Mm. rhomboideus. It is wide near its origin but string-like. The insertion of M. latissimus dorsi metapatagialis is becomes thinner towards the insertion, which is on the caudal on the caudal portion of M. serratus superficialis metapatagialis (dorsal) crest of the middle of the humerus. (Hudson et al., 1972).

M. latissimus dorsi caudalis M. supracoracoideus (Figure 14) This muscle was damaged in this specimen, and we could M. supracoracoideus has a fleshy origin on the sternal not confirm the origin and insertion. The following description carina, sternal body, sternal notch membrane, and the cranial complements Hudson et al. (1972) with respect to the damaged (ventral) surface of the coracoid. It is a large, thick muscle, deep area. to M. pectoralis thoracica and in contact with M. coracobrachialis The origin of M. latissimus dorsi caudalis covers a large caudalis laterally. The muscle belly becomes a thick tendon as dorsal area and can be divided into two parts. One part originates it passes through the triosseal foramen, which consists of the on the spinal processes of the posterior thoracic vertebrae and furcula, scapula, and coracoid. It finally inserts on the dorsal has a sheet-like, aponeurotic origin. The other portion has a tubercle, which is on the dorsal surface of the proximal humerus. fleshy origin on thoracic ribs II-V and the cranial margin of the Although the origin is similar to the superficial M. pectoralis ilium. These muscular bundles run anterolaterally. It is deep to thoracica, the actions of these muscles are completely different. 20 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

M. supracoracoideus generally powers the upstroke of the wings. the humerus. In birds, it consists of Mm. deltoideus major (the M. supracoracoideus elevates and externally rotates the humerus powerful, long, superficial muscle) and minor (the small, short, in European starlings and pigeons (Poore et al. 1997). This deep muscle. Both abducted and flex (protract) the humerus muscle also might perform similar action in Eudromia based on at the glenohumeral joint. The M. deltoideus propatagialis lies its insertion point on humerus and line of action. This muscle superficial to Mm. deltoideus major and minor but does not is complimented by M. pectoralis thoracica, which powers the insert onto the humerus. Instead, it becomes the propatagialis. downstroke assisted by the acrocoraohumeral ligament (Baier, 2007). M. deltoideus major M. deltoideus major has a fleshy origin on the acrocoracoid M. scapulohumeralis cranialis process of the coracoid. The origin is deep to pars propatagialis The scapulohumeralis cranialis is small and thin, and has and superficial to M. deltoideus minor. Its fleshy insertion is on a fleshy origin on the anterodorsal margin of the scapula. The the dorsal surface of the proximal humerus. muscle runs dorsal to the scapula, and has a fleshy insertion onto the proximal humerus. It contacts M. scapulohumeralis caudalis M. deltoideus minor caudally. The action of this muscle is adduction and extension at M. deltoideus minor has a fleshy origin on the dorsal the glenohumeral joint, but the force might be weak because the apex of the furcula and the acrocoracoid process. It covers the muscle belly is very thin. articular capsule of the glenohumeral joint, and inserts on the dorsal surface of the humerus, proximal to the insertion of M. M. scapulohumeralis caudalis (Figure 13) deltoideus pars major. M. scapulohumeralis caudalis is relatively large, and has a Sullivan (1962) proposed that this muscle should be fleshy origin that nearly covers the entire lateral surface of the termed M. coracobrachialis cranialis, because it develops from scapula. The muscle runs anterolaterally, deep to M. latissimus the ventral mass embryologically. However, Sullivan (1962) dorsi cranialis. Its cranial margin contacts M. scapulohumeralis was referring to a different muscle than M. deltoideus pars cranialis, and the caudal margin contacts M. latissimus dorsi minor, which is M. coracobrachialis cranialis. caudalis. It inserts onto the ventral tubercle of the humerus with strong tendon, distal to the insertion of M. scapulohumeralis M. deltoideus propatagialis cranialis. The action of this muscle is adduction and extension M. deltoideus propatagialis has a fleshy origin on the of the humerus at the glenohumeral joint, retracting the humerus dorsal apex of the furcula. This thin muscle is superficial to M. posteromedially. deltoideus major and extends the propatagialis. The tendon of propatagialis is a long, elastic connective tissue with muscles M. subscapularis (Figure 13) spanning between the shoulder and the radiale. In addition, M. subscapularis is divided into medial and laterale heads birds also have a similar structure, the metapatagialis spanning and have fleshy origins on the medial and lateral side of the between trunk and elbow. Birds obtain lift during flying proximal scapula, respectively. These heads are fused just below by expanding the propatagialis on the leading edge and the the ventral margin of the scapula; both heads are, therefore, very metapatagialis on the trailing edge of the wings (Raikow, 1985). short. The muscle belly immediately forms a common tendon Embryological evidence suggests this muscle might be related to with M. subcoracoideus, which inserts onto the ventral tubercle other deltoideus muscles (Sullivan, 1962), but it functions very of the humerus. differently. The muscles inserting onto the propatagialis tendon are M. subcoracoideus (Figure 13) M. cucullaris capitis, M. pectoralis, M. biceps brachii and Mm. The fleshy origin of M. subcoracoideus is on the lateral deltoideus major and minor (Baumel et al., 1993). These slips, surface of the rostrum sterni and the medial surface of the including M. deltoideus, tauten the propatagialis tendon. sternocoracoclavicle membrane. This powerful muscle runs medially and dorsally to the coracoid, but does not attach to Acrocoracohumeral ligament (Figure 15) the coracoid. The muscle becomes a common tendon with The acrocoracohumeral ligament is a mediolateally broad, M. subscapularis and inserts onto the ventral tubercle of the but relatively thin ligament running from the acrocoracoid humerus. It is deep to M. biceps brachii near its insertion. M. process of the coracoid and the cranial side of the proximal subscapularis and M. subcoracoideus adduct/retract the humerus humerus. Recently the role of this ligament has been reassessed. at the glenohumeral joint. This ligament remains taut through downstroke and most of upstroke, while becoming slack during the transition from Mm. deltoideus (Figure 15) downstroke to upstroke (Baier, 2012). When M. pectoralis M. deltoideus extends from the scapula and furcula to thoracica contracts to produce the downstroke, this force is The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 21

Fig. 16. Musculature of the forearm region of E. elegans, dorsal (extensor) view. (A) Musculature of superficial layer. (B) Musculature of the forearm. M. extensor digitorum communis (EDC) was removed. (C) Musculature of the second layer of the forearm. M. ectoepicondylo-ulnaris, M. extensor metacarpi radialis (EMR) and M. extensor carpi ulnaris (ECU) were removed. (D) Musculature of the deepest layer of the forearm. M. extensor pollicis longus (EPL) was removed. Other Abbreviations in this figure: ECU, extensor carpi ulnaris; EDC, extensor digitorum communis; EPL, extensor pollicis longus; FCU, flexor carpi ulnaris.

counterbalanced by the acrocoracohumeral ligament, which that of M. biceps brachialis. It has a fleshy insertion on a large prevents the shoulder from dislocating (Baier et al., 2007). area of the cranial humeral diaphysis distal to the insertions of M. biceps brachialis and M. pectoralis thoracica. 4. Muscles from shoulder girdle/trunk to humerus, Ventral group M. coracobrachialis caudalis M. coracobrachialis caudalis is large muscle with a fleshy Mm. coracobrachiales (Figures 14, 15) origin on the ventral craniolateral trabecula of the sternum that The avian Mm. coracobrachiales is divided into two parts, extends to the lateral surface of the coracoid and the fascia of M. Mm. coracobrachialis cranialis and caudalis. These muscles supracoracoideus. It inserts tendinously onto the ventral tubercle run between the coracoid and the humerus to adduct and flex of the humerus. humerus at the glenohumeral joint. Generally these muscles are large and divided into two or three slips in reptiles, including M. pectoralis thoracica (Figure 14) birds and other archosaurs, while that of mammals is reduced M. pectoralis thoracica is the largest muscle in volant and composed of a single slip. This difference might be related birds and is the most superficial muscle in the ventral region to the reduction of the coracoid in mammals relative to the of the trunk. It has a fleshy origin that extends onto the sternal condition in reptiles. It is innervated by the medianoulnar nerve carina, intermediate tubercula, sternal notch membrane, and (N. medianoulnaris). ventrolateral surface of the furcula. This muscle has not clear boundary as known as the membrana intramuscularis between M. coracobrachialis cranialis superficial pers sternobrachialis and deep pers thoracobrachialis M. coracobrachialis cranialis has a tendinous origin on the in Eudromia, differing from the condition of other birds (Simic dorsolateral process of the coracoid. The origin is located near & Andrejevic, 1963; Dial et al., 1988). However, the boundary 22 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 17. Musculature of the forearm region of E. elegans, ventral (flexor) view. (A) Musculature of superficial layer of the forearm. (B) Musculature of the forearm, M. pronator superficialis was removed. (C) Musculature of the forearm, M. flexor digitorum superficialis (FDS) was draw forward. (D) Musculature of the forearm, M. pronator profundus was removed. (E) Musculature of the deepest layer of the forearm. M. flexor carpi ulnaris (FCU) and extensor muscles were removed. Other Abbreviations in this figure: EMR, extensor metacarpi radialis; FCU, flexor carpi ulnaris; FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis.

becomes clear at the distal narrow part of M. pectoralis. The propatagialis attaches to the lateral surface of the radiale, as insertion, partly tendinous medially and fleshy laterally, is on the noted above. deltopectoral crest of the humerus probably corrsesponding pers sternobrachialis and thoracobrachialis, respectively. The action M. pectoralis abdominalis of this muscle is flexion of the humerus at the glenohumeral This muscle is probably one of the cutaneous muscles. We joint, which causes the strong downstroke (Dial et al., 1988). It could not find a distinct origin and insertion for this muscle in is innervated by the lateral and medial thoracic nerve. our specimen.

M. pectoralis propatagialis 5. Brachial muscles, Extensors M. pectoralis propatagialis is also referred to as M. tensor propatagialis longus in veterinary anatomy. This muscle M. triceps brachii (Figure 15) originates from the belly of M. pectoralis thoracica, and inserts M. triceps brachii is a highly developed extensor muscle onto the anteroventral margin of the propatagialis tendon. The and is generally divided into three heads in mammals, five in The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 23

Fig. 18. Musculature in the manus region of E. elegans, dorsal view. (A) Musculature and tendons, anterodorsal view. (B, C) Muscle attachment of the pollicis (thumb). (D) Muscle attachment of the indicis (index finger). Other Abbreviations in this figure: EMR, extensor metacarpi radialis; EPL: extensor pollicis longus; EDC, extensor digitorum communis.

Crocodylia (Meers, 2003), and two in Aves (Raikow, 1985). The muscle belly is deep to M. scapulohumeralis caudalis, This muscle in Eudromia is also divided into two heads. One is notched by the pneumatic foramen and the tendon of M. biarticular, M. scapulotriceps, and the other, M. humerotriceps, scapulohumeralis caudalis. The dorsal margin of the belly is monoarticular. The radial nerve innervates them both. M. contacts M. latissimus dorsi cranialis near its origin. M. scapulotriceps extents the ulna at the elbow joint, and M. humerotriceps is divided into a central, large belly and smaller humerotriceps extends the humerus at the glenohumeral joint. slips dorsally (medially) and ventrally (laterally). The ventral and central bellies distally converge onto a common, broad M. scapulotriceps tendon occupying the profundus layer of the tendinous insertion The origin of M. scapulotriceps is divided into two onto the olecranon. The dorsal belly has a fleshy insertion onto tendinous slips on the lateral surface of the scapula. One attaches the tendon. distal to the glenoid fossa, and the other is proximal to the origin of M. scapulohumeralis cranialis. These two tendons are 6. Brachial muscles, Flexors confluent, becoming one belly running parallel to the humeral shaft. The belly of M. scapulohumeralis fuses with that of M. M. biceps brachii (Figure 15) humerotriceps and inserts onto the olecranon. M. biceps brachii is the largest forelimb flexor muscle. The origin is broad and aponeurotic, extending from the anterolateral M. humerotriceps distal coracoid to the bicipital crest of the humerus, and deep to M. humerotriceps originates on the diaphysis of the M. pectoralis thoracica. As in most reptiles, it consists of one humerus. The origin is mostly fleshy, but partially aponeurotic. head, which is broad proximally and narrow distally. It is in 24 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 19. Musculature in the manus region of E. elegans, palmar view. (A) Musculature and tendons, posteroplantar view. (B) Musculature and tendons of the wrist, posteroplantar view. (C) Muscle attachment of the indicis (index finger). (D) Muscle attachment of the palmar. Other Abbreviations in this figure: FCU, flexor carpi ulnaris; FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis.

contact with M. coracobrachialis cranially and M. humerotriceps M. brachialis has a fleshy origin on the distal ventral laterally. There are no muscles in contact with M. biceps brachii epiphysis of the humerus. The belly of this muscle is short, but medially. The insertion attachment is a strong tendon and powerful. The fleshy insertion is on the brachial fossa on the attaches to both the proximal radius and proximal ulna. The ventral proximal ulna. biceps slip, which is a branched small muscle and inserts to the propatagium is absent as described Hudson et al. (1972). 7. Antebrachial muscles, Flexors M. biceps brachii flexes and pronates the forearm at the elbow joint, and it is innervated by the medianoulnar nerve. M. pronator superficialis( Figure 17) M. pronator superficialis has a short tendinous origin on M. expansor secundarium the ventral epicondyle of the humerus. It lies superficial to the M. expansor secundarium is very thin, and was damaged forearm extensors, and the belly lies over M. pronator profundus. when our specimen was skinned. According to Hudson et al. The muscle runs along the radius and inserts onto the distal (1972), the muscle has a tendinous origin on the distal end of M. two fifths of the radial shaft. Hudson et al. (1972) referred this latissimus dors caudalis, ventral edge of M. scapulohumeralis muscle to M. pronator sublimes. caudalis and the posterolateral edge of M. subcoracoideus. The muscle belly is very small and runs along the caudal aspect of M. pronator profundus (Figure 17) M. humerotriceps, and divides into three slips near the olecranon M. pronator profundus has a short tendinous origin on process. It inserts on the proximal three quills of the secondary the medial epicondyle of the humerus distal to the origin of M. flight feathers. pronator superficialis. It runs obliquely across the forearm. The muscle belly fused with M. entepicondylo-ulnaris. The muscle M. brachialis (Figure 17) inserts onto the mid-diaphysis of the radius. The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 25

The distal tendon of M. FDP passes through the cranial M. entepicondylo-ulnaris (Figure 17) groove of the pisiform process, and then divides into two parts.

M. entepicondylo-ulnaris has two origins; one is a short One slip inserts the phalanx of digit I (I1), while the other tendinous origin proximal to the tendinous origin of M. flexor extends to digit II where it fuses with the tendon of M. FDS near digitorum superficialis on the ventral epicondyle of the humerus. the proximal phalanx (II2) and inserts onto the ventral surface of The tendon of M. entepicondylo-ulnaris is deep to the tendon of the distal phalanx. M. pronator profundus. The two tendons are partially fused each other, and therefore could be regarded as a common tendon. The M. ulnometacarpalis ventralis (Figure 19) other origin is on the ventral surface of the ulna. The muscle M. ulnometacarpalis ventralis has a fleshy origin on the belly is deep to M. flexor carpi ulnaris and M. flexor digitorum ventral aspect of the distal diaphysis of the ulna. It is short and superficialis. The muscle has a fleshy insertion on the ventral lies in deep layer of ventral forearm muscles deep to M. FDP. M. aspect of the proximal ulnar shaft. ulnometacarpalis ventralis becomes tendonous near wrist joint and inserts onto the cranial proximal carpometacarpus. M. flexor digitorum superficialis( FDS) (Figure 17) M. flexor digitorum superficialis has a thin tendinous origin 8. Antebrachial muscles, Extensors distal to the tendinous origin of M. pronator profundus on the ventral epicondyle of the humerus. The muscle belly is thin M. extensor metacarpi radialis (EMR) (Figure 16) and deep to M. flexor carpi ulnaris. It is superficial to M. flexor M. extensor metacarpi radialis has a tendinous origin on digitorum profundus. The muscle becomes tendonous near the the dorsal epicondyle of the humerus. The muscle belly is large wrist joint and partially inserts onto the ulnare. This insertion and superficial to other forearm extensor muscles. It contacts M. is via thick, dense connective tissue, and there is no scarring on extensor digitorum communis caudally and M. extensor pollicis the ulnare. Another branch of the tendon runs along the second longus (EPL) distally. The tendon of this muscle runs parallel to digit until it finally inserts onto the ventral surface of the distal the tendon of M. EPL and inserts onto the cranial region of the phalanx of digit II (II2). Hudson et al. (1972) referred this muscle proximal metacarpus I along with M. EPL. The forearm extensor to M. flexor digitorum sublimes. muscles do not extend the elbow, but flex the elbow joint due to their lines of action (Raikow, 1985). The dorsal epicondyle, M. flexor carpi ulnaris( FCU) (Figure 17) which is termed the ectepicondyle or lateral epicondyle in other The origin of M. flexor carpi ulnaris is on the distal ventral animals, faces dorsally, and the insertions of extensors also face epicondyle of the humerus and is the largest of the muscles dorsally. The extensors, therefore, do not pass through the caudal that originate on the ventral epicondyle. It is tendinous near the to the elbow joint. origin and wraps around the ulnar trochlea. It becomes a fleshy belly running along the ulnar shaft. This muscle is superficial to M. supinator (Figure 16) M. flexor digitorum superficialis, M. flexor digitorum profundus, M. supinator originates as a short tendon on the dorsal and M. entepicondylo-ulnaris. The caudal margin of the fascia epicondyle of the humerus. The muscle is deep to and of M. FCU is firmly connected to the base of the secondary completely covered by the tendon of M. EMR and M. EDC, and feathers (Remiges secundariae). It has a tendinous insertion on it inserts on the proximal middle of the radial shaft. the ulnare. M. extensor digitorum communis (EDC) (Figure 16) M. flexor digitorum profundus( FDP) (Figure 17) The tendinous origin of M. extensor digitorum communis The fleshy origin of M. flexor digitorum profundus lies is composed of a thick tendon that originates on the dorsal along the ventral ulnar diaphysis and is part of the deepest layer epicondyle of the humerus and a narrow tendon that originates of forelimb muscles. The proximal portion of M. FDP is deep on the proximal end of the ulna. The origin on the dorsal to the belly of M. pronator profundus and the insertion of M. epicondyle is located distal to the origin of M. EMR and M. entepicondylo-ulnaris. The muscle is relatively large, running supinator. The muscle belly is large near the proximal forearm along the cranial margin of the ulna, and becomes superficial and tapers distally near the mid-diaphyses of the radius and near the middle ulna diaphysis. ulna, becoming tendinous near the distal 20 % of the forearm. The muscle is in contact with M. pronator superficialis and The tendon passes through the extensor retinaculum with the M. pronator profundus cranially (radially) and M. FDS caudally tendon of M. ECU, and divides into thick branches that insert (ulnarly). It contacts M. extensor indicis longus, the deepest onto the dorsal aspect of the caudal metacarpal I. The primary extensor muscle, via the interosseous membrane. M. FDP runs M. EDC tendon passes along a shallow groove on the dorsal between the radius and ulna, and becomes tendinous near the carpometacarpus and inserts onto the distal phalanx of the digit wrist joint. II. 26 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

M. ectepicondylo-ulnaris (Figure 16) M. flexor pollicis( Figure 19) It forms a common tendon with M. extensor carpi ulnaris M. flexor pollicis has a fleshy origin proximally on the at its origin on the dorsal epicondyle. The belly extends to ventral surface of the carpometacarpus. The muscle runs the forearm and inserts onto the anterodorsal surface of the between metacarpal I and the pisiform process. It is small and proximal ulnar shaft. M. ectepicondylo-ulnaris is innervated by lies between M. abductor pollicis and the tendon of M. FDP. It the radial nerve. Hudson et al. (1972) referred this muscle to M. has a fleshy insertion on the caudal margin of the ventral surface anconeus. This muscle is strongly suggested to be homologous of the digit I phalanx. to the extensor ulnaris in crocodiles (Meers, 2003) because of its morphology, relationship to other muscles, and innervation. M. adductor pollicis (Figure 19) The fleshy origin of M. adductor pollicis is on the cranial M. extensor carpi ulnaris (ECU) (Figure 16) margin of the ventral surface of metacarpal II. This muscle runs M. extensor carpi ulnaris has a fleshy origin on the fascia of cranially and inserts onto the first phalanx of digit I and the two M. ectoepicondylo-ulnaris near the middle of the muscle’s belly. quills attached to the allula. M. ECU is very thin. It contacts M. EDC cranially and partially covers M. ectoepicondylo-ulnaris. The muscle belly becomes M. extensor pollicis brevis (EPB) (Figure 18) a tendon near the wrist joint, and the tendon passes through The origin of M. extensor pollicis brevis lies on the cranial the extensor retinaculum with the tendon of M. EDC, finally surface of the proximal metacarpal I. The muscle is short, but inserting onto the dorsal aspects of the caudal carpometacarpus. relatively large. It runs parallel to the tendons of M. extensor pollicis longus (EPL) and M. extensor metacarpi radialis (EMR). M. extensor pollicis longus (EPL) (Figure 16) It has a fleshy insertion on the dorsal surface of the first phalanx

M. extensor pollicis longus has a fleshy origin that extends of digit I (I1) distal to the insertions of M. EPL and M. EMR. from the proximal ulna to the diaphysis of the radius across However, the insertion of M. EPB is highly variable (Hudson et the interosseus membrane ventrally. It is a fairly large muscle al., 1972). Hudson et al. (1972) described M. EPB originating deep to M. supinator, M. EDC, and M. ectoepicondylo-ulnaris from the common tendon of the M. EMR and M. EPL with an proximally. M. EPL can be seen near the distal forearm as M. absent or sometimes slight connection with the carpometacarpus.

EDC reduces in size. Near this region, the muscle lies superficial It inserts on antereior surface of digit I (I1). to M. extensor indicis longus. It becomes tendinous near the wrist joint, and the tendon inserts onto the cranial surface of M. abductor indicis (Figure 18) metacarpal I ventral to the insertion of M. EMR. The fleshy origin of M. abductor indicis is located along the dorsal surface of metacarpal II, extending from the pisiform M. extensor indicis longus (Figure 16) process to the distal edge of metacarpal II. The muscle belly The fleshy origin M. extensor indicis longus lies on has a shallow groove, through which passes the tendon of M. the distal third of the caudal radial diaphysis. The posterior FDP. M. abductor indicis becomes tendinous near the wrist interosseous nerve, a deep branch of the radial nerve, runs along (metacarpophalangeal) joint and inserts onto the proximal dorsal the surface of this muscle. It becomes tendinous near the distal surface of phalanx II1. radius, runs obliquely across the distal articular surface of the ulna, and inserts onto the proximal phalanx of the digit II. M. interosseus dorsalis (Figure 18) M. interosseus dorsalis originates on from the caudal M. ulnometacarpalis dorsalis (Figure 19) margin of metacarpal II to the dorsal caudal margin of The tendinous origin of M. ulnometacarpalis dorsalis lies metacarpal III (the edges of the gap produced by the fused on the cranial margin of the distal ulna. It becomes fleshy as it metacarpals). This muscle is pinnate-form and fills the dorsal runs across the caudal dorsal carpometacarpus and then inserts interosseus space. It is thinner than M. interosseus ventralis. It onto the dorsal surface of metacarpal III. becomes tendinous distally and inserts onto the caudal surface of

phalanx III1. 9. Muscles of Manus M. interosseus ventralis (Figure 19) M. abductor pollicis (Figure 19) The origin of M. interosseus ventralis is located on the The fleshy origin of M. abductor pollicis is near the ventral cranial margin of metacarpal II and the dorsal cranial insertion of M. EMR on metacarpal I. The muscle belly is margin of metacarpal III. It is a pinnate-form muscle and fills relatively large compared to other dorsal intrinsic muscles. It has the ventral interosseus space between metacarpals II and III. It a fleshy insertion on the lateral surface of the digit I phalanx. becomes tendinous near the carpometacarpus-phalanx II1 joint The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 27

Fig. 20. Musculature in the pelvic and thigh region of E. elegans, lateral view. (A) Musculature of the superficial layer of the thigh.( B) Musculature of the second layer of the thigh. M. iliotibialis lateralis was removed. (C) Musculature of the third layer of the thigh. M. iliofibularis was removed. (D) Musculature of the fourth layer of the thigh. M. flexor cruris lateralis was removed. (E) Musculature of the anterior part of the thigh. M. iliotibialis cranialis and iliofemoralis cranialis were removed. (F) Musculature of the deepest layer of the thigh. Mm. caudofemorales and M. flexor cruris medialis were removed. 28 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi and then divides into cranial and caudal tendons. These tendons clear. The belly of M. iliotibialis lateralis is thin mediolaterally insert onto the proximal cranial surfaces of phalanges II1 and and fan-shaped. It is fused with M. femorotibialis lateralis and

II2 respectively. Hudson et al. (1972) referred this muscle to M. intermedius aponeurotically at the anterolateral area of the interosseus volaris, claimed that the caudal tendon was stouter middle of the thigh and inserts onto the lateral cnemial crest of than the cranial tendon. However, these tendons in our specimen the tibia. This muscle cranially contacts the caudal margin of were similar in size, with the cranial tendon being slightly larger. M. iliotibialis cranialis. The middle portion of M. iliotibialis Hudson et al. (1972) also described an attachment to several lateralis is located superficial to M. iliofemoralis externus primary quill follicles, but we could not confirm this attachment. and Mm. femorotibiales. The caudal portion is superficial to the cranial part of M. iliofibularis. The pars postacetabularis M. flexor digiti III( Figure 19) extends the hip joint differently from the pars preacetabularis M. flexor digiti III originates on the ventral surface of because it is positioned caudal to the hip joint. However the metacarpal III. The muscle is small near its origin, but becomes pars postacetabularis assists during hindlimb flexion by active enlarged near its middle. It becomes tendinous near the lengthening (eccentric contraction) to stabilize knee joint (Carr carpometacarpus-phalanx III1 joint and inserts near the caudal et al., 2011a, b). edge of phalanx III1. Baumel et al. (1993) refer to this muscle as M. flexor digiti minoris. Mm. iliotrochanterici (Figure 20) Mm. iliotrochanterici is a large muscle group that occupies Muscles in Hindlimb the cranial iliac fossa and is divided into three portions; M. iliotrochantericus cranialis, medius, and caudalis, as in other 10. Thigh muscles, Extensors birds (Berger, 1952; Klemm, 1969; Raikow, 1970). These muscles produce the internal rotation of the femur, and less Mm. iliotibiales (Figure 20) protraction due to a short lever arm from the center of the hip Mm. iliotibiales are superficial muscles covering the joint (Raikow, 1985). The muscles also play a role in joint cranial surface of the femur. The innervation and location of stabilization (Raikow, 1970). Mm. iliotrochanterici medius and Mm. iliotibiales are very similar to Mm. iliotibiales of non-avian cranialis are fused in Tinamus and Crypturellus, while these reptiles, but these muscles occupy a larger area in the thigh in muscles are not fused in the other tinamous including Eudromia birds than those in reptiles. It is generally divided into three slips (Hudson et al., 1972), as seen in our specimen. in crocodiles and two or three slips in birds. Mm. iliotibiales are Rowe (1986) showed that Mm. iliotrochanterici were separated into two slips in Eudromia—the smaller M. iliotibialis developed from two different anlargens. M. iliotrochantericus cranialis and larger M. iliotibialis lateralis. This muscle group is caudalis develops from a common anlagen with M. mostly innervated by the femoral nerve but also partially by the iliofemoralis externus. The former study also reported that ischiadic nerve. Mm. iliotibiales variably flex or extend the hip Mm. iliotrochanterici cranialis and medialis develop from joint, and extend and abduct the knee joint. same anlagen with M. iliofemoralis internus. In addition, he concluded that Mm. iliotrochanterici pars cranialis and medius M. iliotibialis cranialis are homologous to Mm. puboischiofemoralis internus (PIFI) M. iliotibialis cranialis has a fleshy origin on the in crocodiles because of developmental similarities, although anterodorsal margin of the iliac crest. This muscle covers most Mm. iliotorchanterici originate from the lateral surface of the cranial and superficial part of the thigh. The belly is longer and preacetabular process in birds, and PIFI in crocodiles and M. thicker than M. iliotibialis lateralis. M. iliotibialis cranialis is psoas major in mammals originate on the posterior dorsal and superficial to and covers M. femorotibialis medialis. It inserts lumbar vertebrae, respectively. tendinously onto the cranial cnemial crest of the tibia. M. iliotibialis cranialis was refered to as M. sartorius by Hudson et M. iliotrochantericus medius al. (1972). M. iliotrochantericus medius has a fleshy origin along the the ventrolateral margin of the ilium, cranial to the acetabulum M. iliotibialis lateralis and caudal to M. iliotrochantericus cranialis. The parallelogram- M. iliotibialis lateralis originates on almost the entire shaped belly is the smallest in this group, and it is deep to surface of the iliac crest. It is further divided into two sections. M. iliofemoralis cranialis. The muscle runs caudally with The cranial one-third is referred to as M. iliotibialis lateralis M. iliotrochantericus cranialis. This muscle has a tendinous pars preacetabularis, which is innervated by the femoral nerve, insertion on the anteroventral surface of the femoral trochanter and the caudal two-thirds is referred to as M. iliotibialis lateralis of the femur, ventral to M. iliotrochantericus cranialis and deep pars postacetabularis, which is innervated by the ischiadic to M. iliofemoralis cranialis. nerve. However, the boundary between these muscles is not The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 29

Fig. 21. Musculature in the pelvic and thigh region of E. elegans. (A) Musculature of the superficial layer of the thigh, medial view. (B) Musculature of the second layer of the thigh, medial view. The detached the right lower leg from pelvis. M. ambiens was removed. (C) Musculature of the deepest layer of the thigh, anteromedial view. M. femorotibialis lateralis and intermedius were detached. (D) Musculature of the pelvis, medial view. (E) Musculature of the deepest layer of the thigh, lateral view.

M. iliotrochantericus cranialis posterior (Hudson et al., 1972). This muscle orginates on the M. iliotrochantericus medius has a fleshy origin along the cranial iliac fossa. This muscle is deep to M. iliotibialis cranialis ventrolateral margin of the illium, cranial to the acetabulum. The cranially and M. iliotibialis lateralis proximally. It is the largest origin is located cranial to M. iliotrochantericus medius. The M. iliofemoralis. The belly is distally divided into a superficial muscle belly is triangular and larger than M. iliotrochantericus and deep layer. The deep layer has a strong, tendinous insertion medius, and it is also deep to M. iliofemoralis cranialis. This along the cranial margin of the trochanteric crest, and the muscle inserts tendinously on the anteroventral surface of the superficial layer inserts on this tendinous insertion of the deep femoral trochanter of the femur. layer. M. iliotrochantericus caudalis is innervated by the lumber nerve. M. iliotrochantericus caudalis The iliotrochantericus caudalis is referred to as M. Mm. iliofemorales (Figure 20) iliofemoralis cranialis (Rowe, 1986) or M. iliotrocantericus Mm. iliofemorales run between the ilium and femur. 30 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Baumel et al. (1993) divided this muscle into Mm. iliofemoralis muscle expands laterally to contact with M. femorotibialis externus and internus. The external M. iliofemoralis externus lateralis, and cover M. femorotibialis medialis partially. This is wide but is not very long. The M. iliofemoralis internus is on muscle is covered with M. iliotibialis and M. ambiens. The the medial side of pelvis; it is small, weak muscle. There are muscle belly is fused with M. femorotibialis lateralis near the many synonyms of M. iliofemoralis interenus, such as M. iliacus distal femur, while the insertion tendon of M. iliofemoralis (Hudson et al., 1972) and M. cuppedicus (Rowe, 1986). cranialis runs between M. femorotibialis intermedius and M. femorotibialis medialis at the point. Distal to the point of fusion, M. iliofemoralis externus the lateralis and intermedius form a strong tendon that inserts on M. iliofemoralis externus has a fleshy origin on the caudal the lateral cnemial crest of the tibia. margin of the iliac crest. This muscle is deep to M. iliotibialis cranially and M. iliofibularis caudally. The shape of the belly M. femorotibialis medialis is trianglular. This muscle has tendinous insertion on the M. femorotibialis medialis is an independent muscle and trochanteric shelf, which is located on the proximolateral surface has a fleshy origination that spans from the proximolateral of the femur. The insertion area is deep to M. femorotibialis portion of the femoral shaft to the preacetabular process. This medialis. M. iliofemoralis externus is innervated by the muscle is deep to M. femorotibialis intermedius and M. ambiens ishchiadic nerve. Hudson et al. (1972) regarded this muscle as M. cranially. It has a tendinous insertion on the cranial cnemial crest glutaeus medius et minimus. of the tibia.

M. iliofemoralis internus M. ambiens (Figure 21) M. iliofemoralis internus is referred to as M. cuppedicus M. ambiens has a fleshy origin on the pectineal process by Rowe (1986), and M. iliacus by Hudson et al. (1972). of the pubis. It is a superficial muscle on the medial side of According to these authors, this muscle has a fleshy origin on the thigh. It is a relatively thin muscle. It runs between M. the ventral margin of the ilium and has a fleshy insertion on the femorotibialis intermedius and M. femorotibialis medialis, posteromedial surface of the proximal shaft, located medially to becomes a thin tendon, and passes deep to the patellar tendon. It both Mm. iliotrochanterici cranialis and medialis. However, this inserts onto the tendinous origin of the lateral head of M. flexor muscle was absent in two specimens of E. elegans. perforatus digiti II. M. ambiens is innervated by the femoral nerve. Mm. femorotibiales (Figures 20, 21) The Mm. femorotibiales group, innervated by the femoral 11. Thigh muscles, Flexors nerve, is a large group of muscles that originate from the cranial, lateral, and medial surfaces of the femoral diaphysis and insert M. iliofibularis( Figure 20) on to the cranial cnemial crest of the tibia. Baumel et al. (1993) The cranial half of M. iliofibularis originates on the divided this muscle into three parts from lateral to medial side in superficial fascia and tendon of M. iliofemoralis externus and birds: Mm. femorotibiales lateralis, intermedius, and medialis. M. the caudal half originates from the tubercle of the caudal iliac femorotibialis lateralis and intermedius are separated proximally crest. Its cranial margin contacts M. femorotibialis lateralis. The and are fused distally, while M. femoralis medialis is the thinnest caudal margin is strongly united with the superficial fascia of and only independent slip of Mm. femorotibiales, located deep M. flexor cruris lateralis. The ischiadic nerve and femoral artery and medially. and vein pass along the cranial deep layer of M. iliofibularis, and the ischiadic nerve then innervates the muscle. The belly is M. femorotibialis lateralis large and tapers distally. It becomes tendinous at the distal thigh M. femorotibialis lateralis has a fleshy origin that covers and passes under the ligamentous ansa m. iliofibularis near the the entire lateral surface of the femoral diaphysis. It is deep proximal end of the fibula. The common fibular nerve, which is to M. iliotibialis medialis and contact with M. femorotibialis a branch of the ischiadic nerve, also passes under the ansa m. intermedius cranially. M. femorotibialis lateralis becomes the iliofibularis. M. iliofibularis inserts on the proximal fibular shaft. short femorotibial tendon with the intermedius inserting onto the This muscle is a major hip extensor and knee flexor. uH dson et cranial cnemial crest of the tibia. Hudson et al. (1972) noted that al. (1972) used the inappropriate (mammalian) name M. biceps this muscle part was uniquely long in Eudromia compared to femoris for M. iliofibularis. other tinamids. M. flexor cruris lateralis( Figure 20) M. femorotibialis intermedius M. flexor cruris lateralis is a large muscle that is divided M. femorotibialis intermedius has a fleshy origin that into two parts: Mm. flexor cruris lateralis pars pelvica and pars covers the cranial surface of the femoral diaphysis, but this accessoria. It is deep to M. iliotibialis. M. flexor cruris lateralis The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 31 was called M. semimembranosus and M. semitendinosus by Hudson et al. (1972) conclude that M. caudofemoralis Hudson et al. (1972). pars caudalis (M. piriformis Pars caudifemoralis) is absent in Eudromia, but this muscle is present in our specimen. The M. flexor cruris lateralis pars pelvica muscle originates on the last two or three free caudal vertebrae M. flexor cruris lateralis pars pelvica originates on the and the uropygium. The origin does not extend onto the caudal part of the ilium and lateral side of the first to forth caudal pygostyle. The proximal portion is deep to M. flexor cruris vertebrae. The belly is thick and wide proximally, but becomes lateralis. The thin belly runs along the ventral margin of the thinner and narrower distally. M. flexor cruris lateralis pars pelvis. This muscle forms a thin common tendon with M. pelvica fuses with M. flexor cruris lateralis pars accessoria near caudofemoralis pars pelvica and inserts on caudal surface of the the distal femur and forms a large belly that then divides into proximal femur. M. caudofemoralis pars caudalis likely flexes three slips. One slip fuses with the fascia of the intermedial head the uropygium rather than retracts the femur because if its small of M. gastrocnemius and with M. flexor cruris medialis. Another size, but this speculation has not been tested experimentally. slip extends to the caudal side of the tibiotarsus where it has a fleshy insertion on the flexor fossa, and the final slip partially M. caudofemoralis pars pelvica becomes a thin aponeurosis, inserting on the proximal tibiotarsus M. caudofemoralis pars pelvica has a fleshy origin on caudal to the insertion of the medial collateral ligament. This the dorsal surface of the caudal iliac crest, ventrocaudal to muscle is innervated by the ischiadic nerve. the origin of M. iliofibularis. The parallelogram-shaped belly of M. caudofemoralis pars pelvica is thinner than that of M. M. flexor cruris lateralis pars accessoria caudofemoralis pars caudalis. The ischiadic nerve and ischiadic M. flexor cruris lateralis pars accessoria has a broad fleshy artery emerge onto the superficial surface of the muscle through origin on the caudal side of the distal femoral shaft. The belly is the ilio-ischiadic fenestra that is located in the middle of the thin but broad. The insertion is the muscle belly of the M. flexor belly. The proximal and distal portions are deep to M. flexor cruris lateralis pars pelvica, forming aponeurotic raphe, near the cruris lateralis and M. iliofibularis, respectively. This muscle has distal femur. a common fleshy insertion on the caudal surface of the proximal femur with M. caudofemoralis pars caudalis. Hudson et al. (1972) M. flexor cruris medialis( Figure 20) noted that this muscle is developed in Tinamidae, but it is very M. flexor cruris medialis has a fleshy origin on the caudal thin in our specimen. end of the pubis and the puboischiadic membrane. The proximal part of the muscle is deep to M. caudofemoralis and is distally M. ischiofemoralis (Figure 20) deep to M. flexor cruris lateralis. The width and thickness of the M. ischiofemoralis has a fleshy origin on the ischium, the muscle is constant along the length. It fuses with M. flexor cruris pubis, and the ilioischiadic membrane. This muscle is deep to M. lateralis at the distal thigh and inserts onto the intermedial head caudofemoralis pars caudalis around its origin on the ischium of M. gastrocnemius. The muscle is innervated by the ischiadic and M. caudofemoralis pars pelvica at the middle of the belly. nerve. It is a very large muscle that runs craniocaudally. The muscle belly becomes a strong tendon anterodistally and inserts onto the M. caudoiliofemoralis (Figure 20) lateral surface of the proximal femur. The tendinous insertion of M. caudoiliofemoralis is small and thin muscles in birds M. iliofemoralis externus is superficial to the tendinous insertion because the caudal vertebrae in birds are highly reduced. This of M. ischiofemoralis. This muscle is innervated by the ischiadic muscle is divided into M. caudofemoralis and M. iliofemoralis nerve, which extends from the caudal surface of the femur. (Baumel et al., 1993). However, we used “M. caudofemoralis pars caudalis/pelvic” here, to avoid the confusion of this M. Mm. obturatorius (Figure 21) iliofemoralis with other thigh muscle, such as M. iliofemoralis Mm. obturatorius is a muscle group that passes through internus/externus. It was suggested that M. caudofemoralis the obturator foramen, which is composed of the proximal pubis pars caudalis and pars pelvica have a common anlagen based and ischium. This muscle group is divided into the larger M. on studies of chicken embryology (Romer, 1927; Vanden- obturatorius medialis and smaller M. obturatorius lateralis. This Berge, 1982). Hudson et al. (1972) referred to this muscle as M. muscle group is innervated by the obturator nerve. piriformis and to as pars caudofemoralis and iliofemoralis. The pars pelvica seems to attain an origin on the ischia secondarily. M. obturatorius medialis The above two parts make a common tendon and inserts on the M. obturatorius medialis has a fleshy origin on the lateral side of the proximal femur. medial surface of the ilium, ischium, and pubis, as well as the ilioischiadic and ischiopubic membrane. It is the only large M. caudofemoralis pars caudalis muscle that originates on the medial surface of the pelvis. The 32 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 22. Musculature in the crural region of E. elegans, anterior view. (A) Musculature of the superficial layer of the crus. (B) Musculature of the second layer of the crus, anteromedial view. The medial head of M. gastrocnemius was removed. (C) Musculature of the second layer of the distal crus. (D) Musculature of the deepest layer of the crus, anterior view. M. fibularis longus and tibialis cranialis were removed

muscle runs cranially, tapering from its origin to its insertion. pars lateralis) and medial (M. pubo-ischo-femoralis pars After this muscle passes through the obturator foramen, M. medialis) heads (Baumel et al., 1993), but these heads are obturatorius lateralis attaches to M. obturatorius medialis. The difficult to differentiate in tinamids. In Eudromia, there appears muscle becomes a strong tendon distally and inserts onto the to be only a single head of this muscle, which is trapezoidal in proximolateral surface of the femur. shape. It inserts onto the caudal surface of the distal femur. The proximal half of this insertion is fleshy, and the distal half is M. obturatorius lateralis tendinous. It is innervated by the obturator nerve. Hudson et al. M. obturatorius lateralis is a very small muscle that (1972) referred to this muscle as M. adductor longus. originates on the lateral surface of the pubis, cranial to the obturator foramen. It runs deep to the tendon of M. obturatorius 12. Crural muscles, Extensors medialis. A proximal part of this muscle inserts onto the tendon of the internus, and a distal part has a fleshy insertion on the M. tibialis cranialis (Figure 22) lateral surface of the proximal femur, caudal to the insertion of M. The origin of M. tibialis cranialis is generally divided obturatorius medialis. M. obturatorius lateralis is innervated by into a femoral head and a tibial head in birds, in which the the obturator nerve. femoral head has a tendinous origin on the cranial surface of the lateral condyle of the femur, and the tibial head originates M. pubo-ischio-femoralis (Figures 20, 21) on the proximal tibiotarsus (Cracraft, 1971; McGowan, 1979). M. pubo-ischio-femoralis has a fleshy origin that Hudson et al. (1972) also described the presence of two heads in extends from the pubic to the ischium along the puboischiadic timanids, but the femoral head of M. tibialis cranialis is absent in membrane. It is composed of lateral (M. pubo-ischio-femoralis our specimens. The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 33

Fig. 23. Musculature in the crural region of E. elegans, posterior view. (A) Musculature of the superficial layer of the crus, posteromedial view. (B) Musculature of the second layer of the crus, posteromedial view. The medial head of gastrocnemius was removed. (C) Musculature of the second layer of the crus, posteromedial view. The lateral head of M. gastrocnemius was removed. (D) Musculature of the superficial layer of crus, posterolateral view. The lateral head of M. gastrocnemius was removed. (E) Musculature of the superficial layer of the crus, posterolateral view. M. fibularis longus was removed.( F) Musculature of the superficial layer of the crus, showing the structure of FP IV and III. M. FPPII and III are removed. (G) The musculature of the second layer of the crus. FPII, III, and IV were removed. (H) The deep musculature of the popliteal region. M. FHL and FDP were removed. Other Abbreviations in this figure: FDP, flexor digitorum profundus; FHL, flexor hallucis longus; FP, flexor perforates; FPP, flexor perforans et perforatus

The tibial head of the M. tibialis cranialis is divided into spans across fascia, the bony muscle scar does not reflect the a medial and a lateral slip. Both slips have fleshy origin on true shape and size of the muscle’s origin. The medial slip is the lateral surface of the lateral cnemial crest and the fascia roughly twice as thick as the lateral slip and develops a strong of M. EDL, respectively. Because the origin of the lateral slip fascia proximally. Both slips are immediately fused and deep 34 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

Fig. 24. Musculature in the pes region of E. elegans. (A) M. fibularis brevis. The inset shows the tendon and insertion of M. fibularis brevis. (B) Musculature of superficial layer of the pes. The tendon of M. extensor digitorum longus was shifted to show the deeper layer. (C) Musculature of the deepest layer of the pes, dorsal view. The tendon of M. extensor digitorum longus was removed. The inset shows the lateral view of the pes. M. abductor digiti II was shown. (D) The plantar view of pes. The tendon of FP II was penetrated by the tendon of FPP II. And the FPP II was penetrated by the tendon of FDP (not shown). The Achilles tendon was removed. (E) The plantar view of pes. The tendon of FP III was penetrated by the tendon of FPP III. And the FPP III was penetrated by the tendon of FDP. (F) Musculature of the deepest layer of the pes. The common tendon of M.FDP and FHL were removed.

to M. fibularis longus. It becomes tendinous around the distal the distal 1/5 of the tibiotarsus, and it runs along the lateral 3/4 of the tibiotarsus, running deep to M. extensor retinaculum. side of the tendon of M. tibialis cranialis, deep to M. extensor The distal tendon becomes thick and divides into two parts and retinaculum, and through the foramen for M. EDL, which is inserted on the proximal 1/5 of the tarsometatarsus. This muscle located on the distal tibiotarsus. The tendon of this muscle splits is innervated by the deep fibular nerve. into tendons that extend to digits II (tendon TII), III (TIII), and IV

(TIV). The TII additionally is divided further into two tendons, M. extensor digitorum longus (Figure 22) and these tendons insert onto the extensor hood (a sheath-like

M. extensor digitorum longus (EDL) originates on the covering) of phalanges II2 and II3. TIII also divided into two lateral surface of the cranial cnemial crest. The belly is large, tendons that insert on the extensor hood of phalanges III3 and but not as thick as M. tibialis cranialis. This muscle is largely III4. TIV inserts on the extensor hood of phalanges IV4 and IV5. covered by M. tibialis cranialis. It becomes tendinous near This muscle is innervated by the deep fibular nerve. The origin of The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 35

M. EDL in birds is different from its origin in crocodiles, which contacts FPP III laterally, and is deep to FPP II. The pars lateralis arise from the cranial surface of the distal femur (Hutchinson, of M. gastrocnemius becomes tendinous at the distal 1/4 of the 2002). tibiotarsus, and then fuses with the distal tendon of the medial head. The lateral head of M. gastrocnemius flexes the knee joint Mm. fibulares (Figures 22, 24) and plantar flexes the ankle joint. Mm. fibularis (or Mm. peroneus) is divided into Mm. fibularis longus and brevis. A lateral branch of M. EDL branches Pars medialis is referred to as M. fibularis tertius in some mammals, but it is The pars medialis has a fleshy fleshy origin on the fascia absent in birds. M. fibularis longus is distinctly larger than M. of M. femorotibialis medialis and the medial surface of the fibularis brevis in crocodiles and birds, but this difference is cranial cnemial crest of the tibiotarsus. In addition, there is a more exaggerated in birds. These muscles are innervated by the separate origin on the medial diaphysis of the tibiotarsus that is superficial fibular nerve. posterodistally long and craniocaudally thin. It has a very large belly that covers the posteromedial and cranial sides of the crus. M. fibularis longus The medial head contacts M. fibularis longus on the cranial This muscle has a fleshy origin that extends along the side of the crus and becomes tendinous at the distal 1/4 of the cranial surface of the fibula, the medial crest of the tibiotarsus tibiotarsus. The medial head fuses with the intermedial head and the fascia of M. tibialis cranialis M. fibularis longus in birds at the midshaft of the tibiotarsus, proximal to the fusion of the is much more developed than in other animals, extending along medial and lateral heads. The medial head of M. gastrocnemius the lateral and cranial surfaces of the crus. The belly is wide, causes plantar flexion of the ankle joint. but relatively thin. The belly drastically narrows, becoming tendinous near the distal crus. The tendon is divided into two Pars intermedia slips. One slip inserts onto the posterolateral surface of the tibial The pars intermedia has a fleshy origin on the proximal cartilage and the other merges with the tendon of M. FP III. lateral epicondyle of the femur. It is much smaller than the other two heads. It becomes tendinous at the proximal 1/3 of M. fibularis brevis the tibiotarsal shaft and fuses the belly of the medial head, M. fibularis brevis in our specimen is exteremely small. thereby following a similar path to the insertion on the caudal This muscle has a fleshy origin on the lateral surface of the tarsometatarsus. The intermedial head of M. gastrocnemius fibular shafts, slightly proximal to the midshaft. The belly flexes the knee joint and plantar flexes the ankle joint. is short and becomes tendinous distally. The tendon passes through the peroneal retinaculum, wraps around the lateral Ansa iliofibularis( Figure 23) malleolus, and inserts on the posterolateral edge of the proximal Ansa iliofibularis is a connective tissue that wraps around tarsometatarsus. the tendinous insertion of M. iliofibularis mediolaterally. It originates from the proximal to the lateral epicondyle of the 13. Crural muscles, Flexors femur and inserts on the lateral fascia of the lateral head of M. gastrocnemius. M. gastrocnemius (Figure 23) The origin of M. gastrocnemius is divided into the pars M flexores perforans et perforatus digiti II( FPP II) (Figure 23) lateralis, intermedia and medialis. This muscle is the largest M. flexores perforans et perforatus digiti II (FPP II) has a muscle in the crus, covering nearly the entire circumference fleshy origin on the lateral epicondyle of the femur, the proximal of the crus, excluding cranial surfaces. The pars lateralis and fascia of the lateral head of M. gastrocnemius, and the patellar medialis do not fuse as a muscle belly, but as a tendon. The tendon. The belly is deep to the lateral head of M. gastrocnemius, tendon of M. gastrocnemius inserts onto the tibial cartilage and it partially covers M. FPP III. This muscle contacts M. (Cartilago tibialis), which is attached to the caudal (plantar) iliofibularis and M. FP IV medially. The muscle belly is thin surface of the proximal tarsometatarsus. M. gastrocnemius is and short. The belly becomes tendinous near the distal 1/4 of innervated by the tibial nerve. the tibiotarsal shaft. The tendon runs slightly obliquely to the long axis of the tibiotarsus and passes along the medial side of Pars lateralis the tibial cartilage with M. FDL. The tendon dives deeper to The origin of the pars lateralis is divided into a superficial the tendon of M. FP II at the middle of the tarsometatarsus. The and deep layer. The superficial layer has fleshy origin on the tendon passes through the two slips of the tendon of M. FP II, lateral epicondyle of the femur, and the deep layer has thick and then divides into a medial and lateral tendon, through which tendinous origin on the lateral epicondyle. The tendon of the M. FDL passes. The medial tendon fuses with M. FP II and deep layer is fused with ansa iliofibularis. The muscle belly inserts on the ventral surface of phalanx II2. The smaller lateral 36 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

tendon inserts on the proximoventral phalanx II3. cartilage. The tendon of M. FP II is then divided into a lateral and medial tendon, through which the tendons of M. FPP III and M. flexores perforans et perforatus digiti III (FPP III) (Figure 23) M. FDP pass near the distal tarsometatarsus. The lateral tendon

M. flexores perforans et perforatus digiti III has a fleshy inserts onto the ventral surface of phalanx III2 and the medial and tendinous origin. The fleshy origin arises from the lateral tendon inserts on the ventral surface of phalanx III3. M. FP II is epicondyle of the femur, just distal to the origin of M. FPP II. innervated by the tibial nerve. The tendinous origin arises from the lateral cnemial crest of the tibiotarsus. The muscle slip with the tendinous origin is deep to M. flexor perforatus digiti IV( FP IV) (Figure 23) the lateral head of M. gastrocnemius and M. FPP II. This muscle M. flexor perforatus digiti IV has a medial and lateral head. contacts M. FPP II, the tendon of M. iliofibularis, and M. FP IV. The medial head has a fleshy origin on the caudal surface of the The muscle belly, which is covered with a thick aponeurosis, femoral epiphysis, just proximal to the origins of M. FP II, M. is longer and broader than that of M. FPP II. The muscle FHL, and M. FDL. The lateral head has an aponeurotic origin becomes tendinous at the middle of the tibiotarsal shaft and then on the caudal surface of the fibular shaft. This muscle has a thin penetrates the tibial cartilage along with M. FDL. The tendon but broad belly because both heads merge very close to their passes deep to M. FP III at the middle of the tarsometatarsus. origination. The muscle belly is partially deep to M. FPP III, M. The tendon penetrates the tendon of M. FP III, and then diverges iliofibularis, and ansa iliofibularis. The belly becomes tendinous into a medial and lateral tendon, through which the tendons of at the cranial 3/4 of the tibiotarsal shaft and descends parallel M. FDL pass. The medial tendon fuses with M. FP II and inserts to the tendon of M. FP III. The tendon divides into lateral and on the ventral aspect of the phalanx III3 and the smaller lateral medial slips near the distal tarsometatarsus and is penetrated tendon inserts on the ventral surface of the proximal surface of by the tendon of M. FDL. Both tendons are further divided, phalanx III4. becoming four tendons at digit IV. The lateral-most and medial-

most tendons insert onto the ventral surface of phalanx IV1. The

M. flexores perforatus digiti II( FP II) (Figure 23) other tendons insert on the ventral surface of phalanx IV2. This M. flexor perforatus digiti II has a medial and lateral head. muscle is innervated by the tibial nerve. The large medial head has a common fleshy origin on the caudal surface of the femoral epiphysis with M. FHL and the medial M. plantaris (Figure 23) head of M. FP IV. The lateral head has a tendinous origin on M. plantaris has a fleshy origin on the caudal surface of the caudal surface of the fibular head. The tendon of the lateral the medial proximal tibiotarsus. The muscle belly is very short head serves as the insertion site for M. ambiens. The medial and becomes tendinous as it reaches the proximal 1/3 of the head has larger attachment area than that of the lateral head. tibiotarsal shaft. It descends with the Achilles tendon, passs The muscle belly of M. FP II is thin, deep to M. FP digiti III and through the thick tibial cartilage (similar to M. gastrocnemius), superficial to M. FHP. It becomes tendinous and runs along the and inserts on the caudal surface of the proximal tarsometatarsus. tarsometatarsus with the tendon of M. FDL. The tendon divides The tibial nerve innervates M. plantaris. near the distal tarsometatarsus and is penetrated by M. FPP II and M. FDL. The medial tendon merges with the tendon of M. M. flexor hallucis longus( FHL) (Figure 23)

FPP III and inserts onto the ventral surface of phalanx II1 and M. flexor hallucis longus has a tendinous origin on the the lateral tendon inserts onto the ventral surface of the proximal caudal surface of the medial femoral epiphysis that it shares with phalanx II2. M. FP II and M. FDL. The short proximal tendinous portion of the muscle passes between the lateral and medial condyles of M. flexor perforatus digiti III( FP III) (Figure 23) the tibiotarsus and becomes fleshy at the tibiotarsal midshaft. M. flexor perforatus digiti III has a medial and a lateral It becomes tendinous again distally as it approaches the distal head. The large medial head has a fleshy origin on the caudal 1/3 of the tibiotarsal shaft. The tendon runs deep to the Achilles surface of the femoral epiphysis, cranial to M. FP IV, and it tendon, changes direction at the medial malleolus, and makes surrounds the caudal tibial artery and fibular artery. The lateral a thick plantar fascia with the tendon of M. flexor digitorum head has a fleshy origin on the deep fascia of M. FP IV. The longus. The plantar fascia divides into three branches at the medial head is fusiform and relatively large, and it is larger than distal tarsometatarsus. Each branch penetrates the tendons of the belly of M. FP IV. The belly of the medial head becomes a Mm. FP and Mm. FPP on digits II and III, and the tendons of tendinous at the cranial 2/3 of the tibiotarsal shaft. The muscle M. FP IV on digit IV. Finally, each branch inserts on the ventral belly of the lateral head is very thin. The lateral head fuses surface of each distal phalanx. M. FHL does not insert on the with the medial head after the medial head becomes tendinous. hallux because this structure is lost in Eudromia. The tendon of M. FP III passes through a tendon sheath at the ankle with M. FP IV and then penetrates the middle of the tibial M. flexor digitorum longus( FDL) (Figure 23) The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 37

M. flexor digitorum longus has a fleshy origin that extends The muscle runs lateral to the tendon of M. extensor digitorum over the caudal surface of the distal epiphysis of the femur, the longus and inserts on the dorsal surface of the phalanx III4. proximal fibular shaft and a large area of the caudal tibiotarsal shaft. Its origin on the distal femur is shared with M. FP II and M. M. extensor brevis digiti III (EB III) (Figure 24) FHL. This muscle lies in the deepest layer. The thin but broad M. extensor brevis digiti III has a fleshy origin on the belly is covered by a thick aponeurosis. It contacts M. flexor medial dorsal surface of the distal tarsometatarsus. The muscle hallucis longus caudally. The belly becomes tendinous near the contacts M. abductor digiti II laterally and M. extensor brevis distal 1/6 of the tibiotarsal shaft. The tendon then passes along digiti IV medially. The muscle has a tendinous insertion on the the medial side of the tibial cartilage, changes the direction dorsal surface of the phalanx III1. at medial malleolus, and fuses with the tendon of M. FHL to produce the plantar fascia. M. extensor brevis digiti IV (EB IV) (Figure 24) M. extensor brevis digiti IV has a fleshy origin along the M. popliteus (Figure 23) dorsolateral shaft of the tarsometatarsus. This muscle contacts M. popliteus has a fleshy, but superficially aponeurotic M. extensor proprius digiti II medially and becomes tendinous origin on the caudal surface of the fibular head. The small near the distal tarsometatarsus. The tendon passes along a bony and short muscle belly runs obliquely to the long axis of the canal between metatarsals III and IV of the tarsometatarsus. The fibula and inserts on the caudal surface of the proximomedial muscle finally inserts on the proximal medial phalanx IV1. tibiotarsal shaft. It lies in the deepest layer of crural muscles along with M. flexor digitorum longus. This muscle is innervated M. abductor digiti IV (Figure 24) by the tibial nerve. M. abductor digiti IV has a fleshy origin laterally on the ventral surface of the tarsometatarsus. It has a tendinous

14. Muscles of Pes insertion proximally on the lateral surface of phalanx IV1.

M. lumbricalis M. flexor hallucis brevis, M. extensor hallucis longus M. lumbricales has a fleshy origin on the dorsal (deep) These muscles are absent in Eudromia due to the loss of surface of the plantar fascia, which is composed of the tendons the hallux. of M. FHL and M. FDL. Baumel et al. (1993) described the muscle bellies of Mm. lumbricales on each digit bilaterally; the DISCUSSION lateral belly is larger than the medial one. In our specimens, the origins of the multiple bellies M. lumbricales were confirmed. General Features of Appendicular Muscular System of Eudromia elegans M. abductor digiti II (Figure 24) M. abductor digiti II has a fleshy origin on the lateral dorsal Unlike other paleognaths, tinamids have flight abilities. tarsometatarsus proximal to digit II. The muscle is short but has The morphological characteristics of tinamids that reflect this a thick belly. It has a tendinous insertion on the proximal ventral difference include a developed sternal carina to support the large surface of phalanx II1. attachment site of M. pectoralis thoracica and winged forelimb capable of flight. Tinamids, therefore, look similar to volant M. adductor digiti II (Figure 24) neognath birds, such as quails or domestic fowl. However, M. adductor digiti II has a fleshy origin on the ventral they also maintain some ancestral characters in their skeleton medial surface of the distal tarsometatarsus proximal to digit III. (Bertelli & Chiappe, 2005), such as elongated lateral trabeculae The muscle belly is narrow but become broader distally. It has a of the sternum (Bledsoe, 1988), an absent rostral external spine tendinous insertion on the lateral margin of the proximal phalanx of the sternum (Parker, 1866), a proximodorsal foramen in the

II1. coracoid (Parker, 1866), the absence of dorsodistal foramina (Bertelli, 2002), a humerus with a shallow transverse ligamental M. extensor proprius digiti III (EP III) (Figure 24) groove (the attachment of acrocoracohumeral ligament; Lee et M. extensor proprius digiti III has a short tendinous origin al., 1997), a ventral condyle longer than the dorsal condyle in on the dorsoproximal metatarsus and on the joint capsule of the the humerus (Clarke & Chiappe, 2001), lack of fusion between ankle tendon. The origin is located proximal to the insertion of M. the distal ilium and ischium (Cracraft, 1974), and a strong, tibialis cranialis, and the proximal tendinous portion of M. EP rounded depression between the tibiotarsal condyles (Bertelli & III passes through the bifurcated tendon of M. tibialis cranialis. Chiappe, 2005). This muscle is thin, and passes along a groove that runs from the In general, the muscular anatomy of tinamids is similar proximal to midshaft of the dorsal surface of the tarsometatarsus. to chickens, as mentioned by Hudson et al. (1972). Our results 38 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi mm ents

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thors Au thors ficiali s O atagiali s O to the shoulder girdle girdle shoulder the to nor

k caudalis profundus craniali s ta p ata g iali s me cranialis O ta p ata g iali s me cranialis O jor ma mi prop cranialis super caudalis caudalis caudalis

ru n m t ro m us fun dus us us Muscle f ora coide bo ide bo ide rhom supe rf icialis rr atus se dorsi latissimus dorsi latissimus scapulohumeralis subscapularis subcoracoideus de lt oideus coracobrachialis rhom atus supe rf icialis rr atus se pro serra tus dorsi latissimus su prac scapulohumeralis coracobrachialis Muscles supe rf icialis rr atus se de lt oideus de lt oideus Table 2. Forelimb muscles of ratites muscles 2. Forelimb Table The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 39

cally Rhea Rhea lo gi nt. sec un in mm ents

has two FCU two heads and insertions in

exp exp is morpho diff ere

1/9 in Emu Emu 1/9 in Emu 2/9 in

ri s ca pula

aput s aput ali s humer aput Synonym Synonym Co

llus va ti on ASUDA Our (2002) (2002) + + Y ob ser

OWA N teryx Ga G (1982) (1982) C M

WE LL ? X O X X O O O O O O O X X O X O ? X O O X X O O O O O O O O X O O O O O O O tr ice ps c O O O tr ice ps c AX (2007) (2007) Drom aius Ap M ti on

X O O X X X X O O O O O O O Our ob serva

va ti on O parts 2 O X O O X O O X X O X O O O O X O O Our ob ser . al et

on ti on +

O O O O O O O O O O O O O O O Our (1972) (1972) Eu dr omi a Struthio Rhea UDSON observa H

thors Au thors to the shoulder girdle girdle shoulder the to ficiali s k arium nd arium

fu ndus

ru n

ec u

m t ro m nar is l m ru m pro Brachial muscles Brachial muscles u yl o-ulnaris Antebrachial muscles muscles Antebrachial Continued. Muscle f li s on d digi to r ato r profundus or at or super or or c arpi

biceps brachii brachii biceps fle x taca rp ali s ulnome ali s ventr pron pulotriceps sca pulotriceps

flex ansor exp ansor bra chia s pectoralis pectoralis abdominalis pectoralis p ro patagialis pectoralis thoracica en tepic digitorum flexor superficialis pron

humerotriceps humerotriceps Muscles Table 2. Table 40 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi EIL EIL EIL EIL nd nd nd nd d d a a n n trich Os trich trich Os trich f a a scle belly scle belly scle be lly scle belly mm ents o in in

PL PL

mm ents

E E EE CU EE CU na

are fused in in are fused Ostrich of the mu are fused in in are fused Ostrich of of in fused ECU are Ostrich. the mu the mu EMR do not reach do not metacarpals. of in fused ECU are Ostrich.

originate from from originate ul the mu

Synonym Synonym Co us Synonym Synonym Co

extensor metacarpi ulnaris

llus va ti on ASUDA Our

llus va ti on (2002) (2002) ASUDA Our + + Y (2002) (2002) ob ser + + Y ob ser

OWA N teryx Ga

G OWA N teryx Ga (1982) (1982) C G (1982) (1982) C M M

WE LL X X O X X O X X O X X O X X O X X O X X O X X O X X O

WE LL O O O X O O O O O longus extensor alulae O O O O O O ancone O O O X X O X X O AX (2007) (2007) AX (2007) (2007) Drom aius Ap M Drom aius Ap M ti on ti on

? O O O O O O O O

Our O X O O O O O X Our ob serva ob serva

va ti on ? O O O O O O O O

va ti on Our O O O O O O O O Our ob ser ob ser . . al al et

et on ti on +

on ti on + O X O O O O O O O

O O O O O O O O Our Our (1972) (1972) (1972) (1972) Eu dr omi a Struthio Rhea UDSON Eu dr omi a Struthio Rhea UDSON observa H observa H

thors Au thors thors Au thors ralis

evis br evis ven t

ngus lo ngus

scles

nar is m ru m III it o Ma nu al mu s llici s s llici s dici s dici s us n iti n Continued. Antebrachial muscles muscles Antebrachial s llici s Continued. rpi ulnaris ca rpi i i po ctor po ctor tor na tor oep icondylo-ul xor dig le xor f flex orpo abdu exten sor intero sseo sseous intero sseous dors ali s abductor indicis abductor indicis addu Muscles extensor pollicis extensor brevis ulnometacarpalis ulnometacarpalis dorsalis exten sor ec t

extensor metacarpi radialis extensor metacarpi Muscles su pi extensor pollicisextensor longus tensor dig ex tensor tensor ex tensor Table 2. Table Table 2. Table The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 41 from the dissection of Eudromia elegans are consistent with Brachial muscles those of Hudson et al. (1972) in almost all respects. However we did find some differences, such as the cranial and caudal Ratites lost the series of muscles related to the pro- and tendon of M. interosseous ventralis were similar in size, rather meta-patagium, including the biceps slip, Mm. deltoideus minor, than the cranial tendon being slightly larger, M. iliofemoralis and M. scapulohumeralis cranialis (Maxwell & Larsson, 2007). internus is absent, the presence of M. caudofemoralis pars M. expansor secundarium is rather developed in Struthio, but pelvica, a thin M. caudofemoralis pars caudalis, and the lack of other ratites lack this muscle and the biceps slip was absent in a femoral head of M. tibialis cranialis. These differences could Eudromia, as well. Almost all brachial muscles in ratites are be attributed to individual variation, but we suggest the absence thin and reduced in volume comparing volant birds, including of M. iliofemoralis internus might be real because both sides of Eudromia. Eudromia has all antebrachial muscles seen in Gallus. the two specimens (the same number as in Hudson et al., 1972) lacked this muscle. Similarly, we consider the absence of the Antebrachial muscles femoral head of M. tibialis cranialis to be real, as well. Eudromia inhabit open grasslands (Davies, 2002), and Struthio has relatively developed antebrachial muscles they are therefore primarily adapted for cursorial locomotion. compared to other ratites, but it has lost three flexor muscles, The hip extensor (Mm. femorotibiales and Mm. iliotibiales) i.e. M. entepicondyle, M. pronator profundus and M. flexor and hip extensor/knee flexor (M. flexor cruris lateralis and M. digitorum profundus. Rhea, Dromaius, and Apteryx have lost iliofibularis) muscles of the hindlimb are highly developed in many flexor and extensor antebrachial muscles. Although the Eudromia. As in most birds, mobility in the trunk of E. elegans antebrachial muscles in ratite are considerably reduced and many is limited due to the fused synsacrum, which contains the last muscles are absent, Struthio maintains many of the antebrachial thoracic, lumbar, sacral, and the proximal caudal vertebrae. The muscles found in other birds. It is known that Struthio frequently preacetabular process is highly developed, providing enlarged use their wings for running away from the predators, mating attachment sites for hindlimb flexor muscles. displays, and to shade chicks (Sauer, 1972). Eudromia maintains all antebrachial muscles seen in Gallus. The Myological Comparison with other ratites Manual muscles The absence and presence of muscles in Eudromia, Struthio, Rhea, Dromius, Apteryx and Gallus are summarized in The manual muscles of Apteryx and Dromaius are Tables 2 and 3. considerably reduced or lost in relation to the reduction of manual bones. All manual muscles shown in Table 2 are absent. Muscles from trunk and shoulder girdle However, Struthio and Rhea retain almost all of these muscles, and the muscles relating to the pollex are well developed. The Many ratites have lost the ability to fly, and this change polluces of these species do not function like the alula in volant in locomotion is reflected strongly their forelimb and wing birds, but they have an increased range of motion, based on the myology. In relation to reduction of wings and forelimbs, the morphology of their first matacarpophalangeal joint. Eudromia muscles of the shoulder girdle and trunk are also reduced. For retains all manual muscles seen in Gallus except for M. extensor example, M. rhomboideus and M. serratus are reduced to some indices brevis, and the muscles related to the pollex are more degree in all ratites. M. rhomboideus superficialis is absent in similar to those of Gallus than Struthio and Rhea. Struthio and profundus is absent in Apteryx (McGowan, 1982). M. serratus superficial metapatagialis is absent in Struthio, Rhea Thigh muscles and Apteryx. M. pectoralis thoracica and M. supracoracoideus have been Compared to the forelimb, the muscles of hindlimb severely reduced in volume. However, M. supracoracoideus are quite developed in ratites. An example is seen in Mm. remains a relatively strong muscle compared to M. pectoralis femorotibiales, which has is very large and branches into thoracica. The positional relationship of these muscles has been more than three parts in all ratites. There is a problem with considerably changed, and the function of these muscles is the terminology M. femorotibialis lateralis (= externus) and different from their antagonist functions during down-stroke and intermedius (= rmedius) (Gangl et al., 2004); the intermedius up-stroke, as seen in volant birds. M. deltoideus minor is absent slip is quite expanded and completely covers the original in all examined ratites, and M. scapulohumeralis cranialis is externus part in many ratites. Some authors, therefore, regarded absent in all examined ratites except for Struthio. this slip as M. femorotibialis lateralis proximal part (McGowan, Eudromia possesses all muscles found in the trunk and the 1979; Patak & Baldwin, 1998; Picasso, 2010). Zinoviev shoulder girdles of Gallus and basal members of Neognathane. (2006) claimed the intermedius shouled be attributed to M. 42 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi ., ., ., .,

al al nd et et

ELLE T li s a M mm ents UDSON UDSON

lateralis lateralis (H Eudromia sen su

media 1972) (1994) (1994)

1972)

present in in present (H absent in absent Eudromia

ris ciali s rf i un dus ris ngus fe mo sus no sus sus no sus sus/ br a no sus/ up e Synonym Synonym Co fe mo atus cto r lo ri us it e nd i it e nd i acili s

nus inter nus se m se m fascia latae & fascia tens or femoris biceps biceps femoris/ femoris/ biceps semimem pars piriformis caudofemoralis

iliofemoralis iliofemoralis piriformis pars pars piriformis qu adr us glute us s rectus

ts par ts llus va ti on ? O ex te rnus O O O O glu te us medius O sarto O X O O addu O prof gluteus O ca ud alis iliofemoralis O O O iliacus, c up pedicus O O gr ASUDA Our (2002) (2002) + + Y ob ser

ts par ts 2 O OWA N O O O O O O O O X O O O O O O O O teryx Ga G (1979) (1979) C M

&

ts par ts 1 O O O O O X O O O O X O O O O O O O ALDWIN ATAK (1998) (1998) P B Drom aius Ap

ts par ts 2 O va ti on O O O O X O O O O O O O X O O part2 O O O O O ICASSO Our (2010) (2010) + + P ob ser

. 20 04)

ts par ts 2 O va ti on O O O O O O O O O O O X O O O O O O ANGLE . ( . Our al + + G ob ser et Eudromia

and 19 72)

ts par ts 3 O va ti on O O O O O O X O O X O O O O O UDSON . ( . Our al Eu dr omi a Struthio Rhea + + H Gallus ob ser et

ica O ria) O dalis O thors Au thors nu s us pe lv ca u vica) ra li s 2 O

cran iali s ca ud alis internus diali s me

(pe l par s par s medi late r ali s cran iali s late (acces so

exte r

li s ralis lateralis lateralis Thigh muscles Thighmuscles eric us eric us eric us fem o is media ur is aris ius or ius ius or ius cr ur is cr ur is cr s iali s s iali s isc hio or fi bu l tr ochant tr ochant tr ochant ti b ti b ura t ura t ub o ili o ili o ili o iliofemoralis ob t ambiens flex ili o flex or caudofemoralis caudofemoralis ischiofemoralis ili o iliofemoralis pectineus ob t ili o flex or p Muscles Table 3. Hindlimb muscles of ratites muscles 3. Hindlimb Table The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 43

ELLE T M mm ents

(1994) (1994)

sen su

Synonym Synonym Co

nus inter nus

intermedia ca ud alis in intermedia Dr omaius

described as described

externus/vastus externus/vastus lateralis

llus va ti on O ASUDA Our (2002) (2002) + + Y ob ser

OWA N teryx Ga G (1979) (1979) C M

&

ALDWIN ATAK (1998) (1998) P B Drom aius Ap

on ti on +

O O O O O O X O O O O O O O O O O O O O O O X X O O O O O O O O O O O X O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O medius/lateralis O O O O O O O O O O ? Our ICASSO (2010) (2010) P observa et

on ti on +

O O O O O O O O O O O O X O O X O 20 04) X X O Our . ( . ANGLE al G observa et

on ti on +

O O O O O O O O O O O O O 19 72) O O Our . ( . UDSON O small O small O small X X O O al Eu dr omi a Struthio Rhea H observa

thors Au thors iali s ra med X

ngus lo ngus cranialis ngus lo ngus ngus lo ngus ngus lo ngus brevis brevis

head

intermedial intermedial

intermedius intermedius O late r ali s acce ss oriu s X diali s me

scle s

ig h mu m ru m Th Crural muscles Crural muscles git o i Continued. d us s halluci s torum digi torum II laris or or lite taris an taris fle x fle x FPP III FPP pl FP IV FP II FPP FP III gastrocnemius gastrocnemius tibialis pop gastrocnemius gastrocnemius lateral head O fi bu fibularis gastrocnemius gastrocnemius sup femorotibialis femorotibialis exten sor femorotibialis femorotibialis femorotibialis femorotibialis Muscles strocnemius ga strocnemius ial h ea d med O Table 3. Table 44 Daisuke Suzuki, Kentaro Chiba, Collin S. VanBuren & Tomoyuki Ohashi

femorotibialis externus pars proximalis in Struthio based on other avian anatomy and previous studies. Also he claimed pars accessorius (sensu Gangl et al., 2004) might be appropriately attributed to the “distal part of M. femorotibialis intermedius.” mm ents

Co These ideas of Zinoviev (2006) are reasonable, but there are

no evidences based on anatomical structure or development

patterns. It is need to investigation of the pelvic and femoral muscle of ratites. In Eudromia, there is no confusion in terminology of Mm. femorotibiales because the intermedius IV

iti part is not as large as that of other ratites. M. femorotibialis intermedius is located “medially,” between M. femorotibialis Synonym Synonym medialis and externus (see Fig. 21C). nsor dig te nsor

M. iliotibialis lateralis in other ratites is broader than that

of Eudromia and Gallus and has a clear border between pars pre-

and post-acetabularis.

llus va ti on Another characteristic of many ratites is a reduced ASUDA Our (2002) (2002) M. iliotrochantericus caudalis, espetially in Strutio and + + Y ob ser . However, and have relatively large M.

Dromaius Rhea Apteryx iliotrochantericus caudalis. While Zinoviev (2006) challenged

OWA N angl ( ) teryx Ga the G et al. 2004 ’s muscular identification; he suggested M. G (1979) (1979) C iliotrochantericus caudalis was fused M. iliofemoralis externus M and Gangl . (2004)’s M. iliotrochantericus caudalis should

et al

& be M. iliotrochantericus medius. Since M. iliofemoralis externus of Struthio has two insertional tendons, and it was odd character ALDWIN ATAK (1998) (1998) P B Drom aius Ap not seen in other aves. If this interpretation is confirmed, the M. iliotrochantericus medialis was not lost in Struthio and the muscle has rather developped. That problem is not applicable on ti on +

O O O O O O O O O X O O X X O O X X X O O O O O O O ? O O O O O X O X to Dromaius X because ex M. iliofemoralis has only one insertional Our ICASSO (2010) (2010)

P tendon. In either case, the reduction of M. iliotrochantericus observa caudalis in Struthio and Dromaius might be real comparing to . that of Eudromia and Gallus (see description). al et

The ratites tend to have diminished or absent M. on ti on +

O O O X X X X O X

Our caudofemoralis pars caudalis, but a developed pars pelvica. In (2004) (2004)

ANGLE addition, M. ischiofemoralis is considerably diminished, except observa G in Apteryx. In Eudromia, M. caudofemoralis pars pelvica is also .

al thinner or absent (Hudson et al., 1972) and is more strongly et

on ti on + developed than M. ischiofemoralis.

O O O X X O O O X Our M flexor cruris medialis in is smaller and has a

(1972) (1972) Struthio Eu dr omi a Struthio Rhea O vestigal O O vestigial O O O vestigial O UDSON shorter belly with a long tendon, compared with its morphology observa H

in Eudromia and Gallus; however this muscle in other ratites, such as Dromaius, Apteryx, and Rhea, is rather similar to that of Eudromia. thors Au thors The hip extensor/knee flexor muscles are also considerably

larger due to enlargement of the postacetabular area of the ilium.

ngus lo ngus evis br evis

Although the number of the thigh muscles is reduced in some ratites due to the missing M. caudofemoralis pars caudalis, II II IV IV is the volume of the muscles is larger than those of volant birds. Pedal muscles iti iti iti iti Eudromia and Gallus also possess well-developed thigh muscles, Continued. hal luc but the proportional volume is smaller than those of other ratites. s halluci s ricalis dig ctor dig ctor dig ctor dig ctor or abdu lumb

Muscles extensor III digiti proprius addu extensor digiti III extensor digiti brevis extensor IV digiti brevis exten sor fle x abdu addu Table 3. Table The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans) 45

Crural muscles ratites (Davies, 2002; Briggs, 2003), which has been supported by recent molecular phylogenies (Slack, 2007; Harshman et Among the crural muscles, the number of the parts and al., 2008, Philips et al., 2010; Smith et al., 2012) and earlier proportional size of M. gastrocnemius is highly variable among morphological phylogenies (e.g., Elzanowski, 1995). In some of the ratites. The terminology is also variable. Struthio, Rhea these analyses, Struthio (the ostrich) is recovered as the outgroup and Dromaius have four heads of this muscle (Gangl et al., to all other palaeognathes, and tinamids are the sister group to 2004; Patak & Baldwin, 1998; Zinoviev, 2006; Piccaso, 2010) the now-extinct moas of New Zealand (e.g., Smith et al., 2012). and Apteryx has three (McGowan, 1979). The general avian This topology suggests that flightlessness may have evolved M. gastrocnemius is divided into three heads, pars medialis, multiple times in palaeognathes, although this hypothesis is less pars lateralis and pars intermedius (Baumel, 1993). The fourth parsimonious than a single reversal in tinamids to the ancestral head, pars supramedialis (sensu Gangl et al., 2004) branches volant state. If tinamous did experience a reversal and are from pars medialis. Patak & Baldwin (1998) named this secondarily volant, they may be a model system for studying fourth slip as intermedia pars caudalis in Dromaius. In Rhea, the evolution of flight in vertebrates. In order for a parsimonious Picasso (2010) used simply “fourth part”, which corresponds hypothesis for character evolution to be rejected, contrary to pars supramedialis. Zinoviev (2006) was claimed this pars evidence of character acquisition is required. In this example, it supramedialis should be attributed M. plantaris because the needs to be shown that all flightless palaeognathes differ in either morphology is similar to M. plantaris of other birds, except for their mechanisms that cause the reduced development of their fusing M. gastrocnemius pars medialis. flight features and/or the anatomy of features ancestrally related The largest slip of M. gastrocnemius in ratites is generally to flight (e.g., wings) to falsify this hypothesis. We hope that our the pars medialis. The pars medialis in Apteryx is 50 % larger anatomical description has allowed for further investigation into than pars lateralis (McGowan, 1979) and a similar condition is the anatomy of one member of Palaeognathae to inspire future seen in Rhea (Picasso, 2010, Fig. 12b). M. gastrocnemius pars research to examine the interesting anatomy of this important medialis in Dromaius is slightly larger than pars lateralis (Patak clade. & Baldwin, 1998, Fig. 6), while pars medialis in Struthio is roughly the same size as pars lateralis (Gangl et al., 2004, our ACKNOWLEDGEMENTS observation). M. gastrocnemius pars medialis does not function as a knee flexor because it originates from the proximal tibia. We wish to thank Dr. Akinori Azumano (Zoorasia These size differences might affect the gait and running. The Yokohama Zoological Gardens), Drs. Kyoko Iwami and Takeshi pars medialis of Eudromia is quite larger than pars lateralis. Yamasaki (Yamashina Institute of Ornithology), Drs. Makoto In addition, many ratites have a reduced hallux, except Manabe and Isao Nishiumi (National Museum of Nature and for Apteryx, and the related muscles are missing. Eudromia has Science), Ryoko Matsumoto (Kanagawa Prefectural Museum of also lost the hallux and some related muscles, such as M. flexor Natural History) for providing the Eudromia specimens. We also hallucis brevis and M. extensor hallucis longus. thank John Hutchinson and an anonymous reviewer for helpful feedback on earlier versions of this manuscript. Phylogenetic Position of Tinamiidae and Future Impication for Evolution of Flight REFERENCES

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