Madrynornis mirandus, Hospitaleche & Tambussi & Donato & Cozzuol, 2007
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publication ID |
https://doi.org/ 10.5281/zenodo.13741859 |
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persistent identifier |
https://treatment.plazi.org/id/03E86754-6041-FFE8-EC4E-F980FD07F9BA |
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treatment provided by |
Felipe |
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scientific name |
Madrynornis mirandus |
| status |
sp. nov. |
Madrynornis mirandus sp. nov.
Figs. 2–7.
Holotype: Madrynornis mirandus , a nearly complete and articulated skeleton, MEF− PV 100, collected by one of the authors ( MC). It includes: skull with partially preserved rostrum, mandible missing distal portion, 27 vertebrae, pygostyle, pelvis, left and right femora, right patella, left and right tibiotarsi and fibulae, left and right tarsometatarsi, 16 pedal phalanges (2 and ungual of second digit, 1, 2, and 3 of third digit, 1, 3, and 4 of fourth digit of the left side; 1 of second digit, 1, 2, 3, and ungual of third digit, and 2, 3, and 4 of fourth digit of the right side), sternum, 13 ribs, right scapula, left and right coracoids, furcula, left and right humeri, right ulna, right radius, right carpometacarpus.
Derivation of the name: From Latin, mirandus , wonderful. From the excellent preservation of the skeleton.
Measurements.—Skull: total length, ca. 145 mm; postorbital width, 51 mm; mandible length, ca. 111 mm; posterior height of mandible, 9.7 mm; height at level of mandibular angle, 15.5 mm. Sternum: total length, 136 mm; width at posterior most costal facet, 66 mm. Coracoid: length, 8.48 mm; distal width, 31 mm. Scapula: length, 114.2 mm; width of articular end, 23.9 mm. Humerus: length, 79.1 mm; distal width, 20.5 mm. Ulna: length, 59.1 mm. Radius: length, 57.8 mm. Carpometacarpus: length, 48.6 mm; proximal width, 15.8 mm. Pelvis: length among midline, 99 mm. Femur: length, 85.9 mm. Tibiotarsus: maximum length, 134.6 mm; distal width, 16.9 mm. Tarsometatarsus: length, 36.5 mm; proximal width, 18.1 mm; distal width, 19.1 mm. Pygostyle: length, 44 mm. Left phalanges (length) of the second digit: 2 (19.4 mm) and ungual (15.6 mm); of the third digit: 1 (25.4 mm), 2 (20.7 mm), and 3 (20.2 mm); and of the fourth digit: 1 (20.2 mm), 3 (14.4 mm), and 4 (14.8 mm). Right phalanges (length) of the second digit: 1 (22.7 mm); of the third digit: 2 (25.6 mm), 2 (21.7 mm), 3 (19 mm), and ungual (18.1 mm); and of the fourth digit: 2 (15.5 mm), 3 (14.4 mm), and 4 (14.8 mm).
Diagnosis.—As for the genus.
Description and comparisons.—Skull: Similar in size to the Adelie Penguin, Pygoscelis adeliae ( Hombron and Jacquinot, 1841) . The cerebellar protuberance projects more distally than the paroccipital process ( Figs. 3A View Fig , 6A View Fig ), while in Pygoscelis antarctica ( Forster, 1781) they project slightly further posteriorly. The paroccipital processes are ventrally directed as in the living species, whereas in Paraptenodytes they are bifid and caudally projected. The transverse occipital crest is expanded posterolaterally and wing−like, similar to Spheniscus , Eudyptes , and Paraptenodytes . The sagital crest (apparent in Paraptenodytes ) is absent in Madrynornis . The occipital region is trapezoidal in shape, but is subcircular in Paraptenodytes and quadrangular in Eudyptes , Eudyptula , and Spheniscus . The temporal fossa is deep and triangular with its dorsal tip not reaching the position of the sagittal crest. The postorbital processes are thin, long ( Figs. 3A View Fig , 6A View Fig ), and project ventrally, whereas in Paraptenodytes they are directed posteriorly. The frontals form a medial crest much narrower than in the living species, and which is absent in Paraptenodytes . The entire jugal arch is gently curved, a characteristic shared with Spheniscus . Extreme curvature of the anterior portion of the arch is a feature of Eudyptes , Pygoscelis adeliae , and P. antarctica , and to a lesser degree of P. papua Forster, 1781 , Megadyptes Milne−Edwards, 1880 , and Aptenodytes (Zusi 1975) . The basitemporal plate is broader than in all the compared species. The pterygoid (narrow and rod−like in Paraptenodytes ) is expanded to form a thin, horizontal plate similar to that seen in extant species. The tomial crest is above the level of the parasphenoidal plate, as in Aptenodytes and Pygoscelis , but is not parallel as in Aptenodytes forsteri Gray, 1844 .
The mandible is straight. The medial process, larger than in Paraptenodytes , bears a medially directed hook−like projection. The caudal fenestra is oval and the rostral fenestra is absent. On the medial surface of the mandible, extending from the medial mandibular fossa to the retroarticular process, appears a deep groove (shallow in Paraptenodytes ).
Vertebrae: An atlas ( Fig. 3D View Fig ), 12 cervical, 7 dorsal, and 7 caudal vertebrae are preserved. The centra of the cervical vertebrae are strongly heterocoelous ( Fig. 3F View Fig ), and have laterally compressed hypapophyses that widen distally. The spinous processes are poorly developed, as in Paraptenodytes . The centra of the dorsal vertebrae are opistocoelous; the caudal vertebrae are platyan ( Fig. 3E View Fig ). The pygostyle ( Fig. 3G View Fig ) is triangular in caudal view and notably larger than in extant species.
Sternum: The costal margin is short, with six deep impressions for the rib insertions. The lateral trabeculae reach the caudal margin, unlike in Spheniscus where the processes extend farther caudally. The sternal rostrum ( Fig. 4D View Fig ) is preserved and shows a closer similarity to Spheniscus than to Pygoscelis .
Furcula: This element is broadly U−shaped, with unflattened clavicles similar to those of Spheniscus . A deep depression (less evident in Pygoscelis ) extends along the dorsal edge.
Scapula: This element is thin ( Fig. 4G View Fig ), broad and more curved than in the living species.
Coracoid: The coracoid foramen is oval as in Aptenodytes forsteri , Eudyptula , and Spheniscus , and is completely closed ( Fig. 4A View Fig ).
Humerus: Intermediate in size between Spheniscus and Pygoscelis , but more slender than in Pygoscelis ( Figs. 4F View Fig , 7A). The degree of torsion between the axis of the head and the flattened plane of the diaphysis ( Simpson 1946) is large in Madrynornis as in Paraptenodytes and the living penguins, and unlike the very small angle seen in other fossil species. The transverse groove is divided in two by a protuberance, as in Paraptenodytes . This tubercle is smaller than in Pygoscelis and narrower than in Spheniscus . The ventral tubercle is very prominent, but smaller than in the fossil species compared. There is a laterally situated fossa on the tubercle as in Pygoscelis adeliae and Spheniscus , whereas in Pygoscelis antarctica it is situated more cranially and is intermediate in Eudyptes (this fossa has not been named to the best of our knowledge). Both ends of the impression of the coracobrachialis cranialis muscle are elliptical, but are rounded in the compared Recent species. The impression decreases in thickness distally, unlike in Spheniscus where it remains the same width throughout its length. The configuration of the trochlear processes ( Figs. 4E View Fig , 7A) is the non− Spheniscus type (O’Hara 1989, 1991): the proximal trochlear process extends beyond the humeral shaft.
The shaft−trochlear angle (between the condyle and the axis of the diaphysis, sensu Simpson 1946) is small (ca. 38 °), but bigger than in Pygoscelis . The impression of the supracoracoideus muscle is oblique to the axis, as in Paraptenodytes , Spheniscus , Eudyptes , and Aptenodytes , although this scar is shorter in the Recent species.
Ulna: This element is similar in size to Pygoscelis . The ventral edge is curved, being straight in Spheniscus .
Radius: The bicipital tubercle is well developed, forming a sharp anteriorly directed projection ( Fig. 4C View Fig ).
Carpometacarpus: The distal end is widest as in Spheniscus , but narrower than in Pygoscelis ( Fig. 4E View Fig ). The dorsal edge is concave as in Eudyptula . In Madrynornis , Spheniscus , and Pygoscelis , the metacarpal major bone is more distally extended than the minor, whereas they are extended equally in Aptenodytes . Both metacarpal bones are more strongly fused and the intermetacarpal distance is much narrower in Eudyptes .
Pelvis: The acetabular foramen is rounded and larger than the oval ilioischiadic foramen ( Fig. 5B View Fig ), as in Eudyptes and Megadyptes . The antitrochanter projects dorsally between them.
Femur: The shaft is straight, as in Spheniscus . The fossa located on the head is moderately deep, similar to Eudyptes and Spheniscus , but shallower than in Paraptenodytes . In caudal view, the trochanter projects almost transversally to the shaft, such as in Pygoscelis . This prominence forms a continuous edge on the caudal surface, that constitutes the antitrochanteric articular facet ( Fig. 5C View Fig ), a feature only present in Pygoscelis adeliae . The trochanter crest extends proximally less than in other extinct species. In external lateral view, the iliotrochanteric impressions are developed over an irregular surface, in contrast to Spheniscus . The cranial intermuscular line extends from those impressions along the cranial surface, as in Paraptenodytes . The obturator impressions are located on a small flattened area, whereas in the extant species, they occupy a well−defined depression. The caudal intermuscular line is less apparent than in Paraptenodytes . The patellar groove is deeper than in the compared species. The strong condylar edges form a deep intercondylar groove, wider than in Paraptenodytes . The medial supracondylar crest is more medial and pronounced than in the compared fossil species. The scar for the insertion of the tendon of the muscle tibialis cranialis muscle is sharp, resembling that of Spheniscus , and is better developed than in Paraptenodytes .
Tibiotarsus: This element is similar in size to that of Pygoscelis papua . The intercnemial groove ( Fig. 5A View Fig ) retains equal depth along its length, as in Spheniscus . The cnemial crest is poorly developed, more so than in Paraptenodytes , and shows a moderate lateral deflection. The flexor fossa is shallow, as in Eudyptula and all the fossils compared. The fibular crest ( Fig. 5A View Fig ) extends over a proportionally greater area than that of Spheniscus and Eudyptes , and is rounded; in Paraptenodytes it is quadrangular. The extensor groove is positioned centrally as in Spheniscus , whereas it is lateral in Aptenodytes . The tubercle where the retinaculi musculi fibularis attaches is barely developed. The condyles are approximately equal in their distal extension, as in Spheniscus and Eudyptula , whereas the medial condyle extends further in Paraptenodytes and the remaining living species. The lateral condyle is elongate and the medial condyle is more or less rounded. Both condyles lack grooves on their margins. An acute edge on the lateral condyle is absent, as in Paraptenodytes . The medial condyle possesses a prominent edge, similar to Pygoscelis and Spheniscus . The lateral epicondylar depression is poorly developed, as in Paraptenodytes . The medial epicondyle is rounded as in Eudyptula .
Fibula: The distal end seems to have been unfused suggesting that the tibiotarsus and fibula were linked synostotically.
Tarsometatarsus: This element is similar in size to that of Pygoscelis papua , although Madrynornis has a larger elongation index. The intercotylar prominence ( Fig. 5D View Fig ) is low and well−rounded. The subcotylar fossa is well developed and triangular, as in Spheniscus and unlike in Paraptenodytes . The medial hypotarsal crest is barely divided (well divided in Paraptenodytes ); there are two intermediate crests (single in Paraptenodytes ) and one lateral crest, as in Paraptenodytes ( Fig. 5D View Fig ). The tuberosity for insertion of the tibialis cranialis muscle are laterally positioned (more central in Paraptenodytes ). The shallow and small medial longitudinal groove is shorter than in Paraptenodytes and does not transversal groove reach the intertrochlear incisure. The lateral longitudinal groove is deeper than in Paraptenodytes , although as in that species neither groove extends as far as the proximal limit of the inscisure. The medial and lateral proximal vascular foramina are unequal in size: the lateral foramen is larger than the medial and exits on the plantar surface (in Paraptenodytes the sub−equally sized foramina both exit plantarly). As in Paraptenodytes , metatarsal fusion is stronger than in Recent species; Eudyptula has the extreme condition with the metatarsals separated by deep furrows. The trochlea of metatarsal II exhibits stronger lateral divergence than in Pygoscelis , Eudyptes , and Spheniscus ; the trochlea of metatarsal III possesses strong, distally divergent trochlear edges, and the trochlea of metatarsal IV is approximately straight and has less distal elongation than Spheniscus .
dorsal tubercle groove coracobrachial impressions tricipital fossa deltopectoral crest ventral tubercle dorsal condyle ventral condyle caudal epiphysys 10 mm lateral vascular proximal foramen intercotylar protuberance hypotarsal lateral cotyle lateral crest medial cotyle dorsal infracotylar fossa medial vascular proximal foramen medial hypotarsal crest lateral groove medial groove trochlea II
Phalanges: There are no fossil phalanges available for comparison with Madrynornis . The 16 phalanges of Madrynornis are similar in shape to those of the living species; they are more robust than those of Spheniscus magellanicus .
| MC |
Museo de Cipolleti |
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