[D] Longipteryx chaoyangensis [~/~]
Zhang, Zhou, Hou and Gu 2001
Cretaceous Early Barremian
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Avialae
Yixian Formation, Liaoning, China
Comment by Mickey Mortimer
\\\"long-wing from Chaoyang City\\\"
(IVPP V 12325) (~190 mm) skull (58 mm), mandible, seven cervical vertebrae, three dorsal vertebrae, nine pairs of dorsal ribs, five uncinate processes, six rows of gastralia, sacrum, four caudal vertebrae, pygostyle, scapulae, coracoids, furcula, sternum (25 mm), four pairs of sternal ribs, humeri (46 mm), radii (41 mm), ulnae (45 mm), radiale, ulnare, semilunate, metacarpal I (4.4 mm), phalanx I-1 (8.5 mm), manual ungual I (7.7 mm), metacarpal II (17 mm), phalanx II-1 (10 mm),phalanx II-2 (9.3 mm), manual ungual II (8.5 mm), metacarpal III (18 mm), phalanx III-1 (5.1 mm), phalanx III-2 (1.5 mm), femora (30 mm), tibiotarsi (32 mm), fibulae (12 mm), metatarsal I (4.8 mm), phalanx I-1, pedal ungual I, metatarsal II (20 mm), phalanx II-1, proximal phalanx II-2, metatarsal III (20.5 mm), phalanx III-1, proximal phalanx III-2, metatarsal IV (21 mm), phalanges from digit IV
(IVPP V 12552) complete skeleton
(IVPP V 12553) furcula, humerus
(IVPP V 12554) ulna
Elongate beak forms over 60% of skull length; forelimb long compared to hindlimb- humerofemoral ratio over 1.6; metatarsal IV longer than metatarsal III.
Description- Although two fairly complete skeletons are known, the text does not indicate which are being described at a given time. Similarily, the figure does not list which specimen is illustrated, although the photo is clearly the holotype. It will be assumed the holotype is described and illustrated in this description. The holotype is approximately 190 mm long, assuming the pygostyle is complete. Certain characters (unfused metacarpus and tibiotarsus) are considered primitive here, while the fused metatarsus indicates some amount of maturity.
The skull is very elongate compared to other basal avians, with a long narrow beak. Most of this is due to the elongate premaxilla. There appears to be a long external naris taking up the posterior two-thirds of the snout. The posterior skull is angled downwards, similar to ornithomimosaurs, and houses enlarged orbits. An interorbital septum is preserved, as is a sclerotic ring of nine elements. The quadrate is double-headed, with a poorly developed orbital process. The mandibular elements are unfused, with a longer dentary and shorter posterior elements than other basal pygostylians, due to the elongate beak. Six teeth are preserved in the premaxilla and maxilla, three in the dentary. They are conical and slightly recurved.
Seven heterocoelous cervicals are preserved. The last three dorsal vertebrae are articulated with the sacrum. At least nine pairs of dorsal ribs are present, with at least five pairs of uncinate processes. The uncinates are not fused to the ribs, slightly expanded distally and decrease in length posteriorly. At least six rows of gastralia are also present. Eight vertebrae make up the synsacrum, the last three of which have the longest transverse processes. Of those three, the longest is on sacral seven. Four free caudals are preserved and have transverse processes. The pygostyle is longer than the four free caudals.
The scapula is blunt distally, while the coracoid is strut-like and appears concave laterally. The furcula is V-shaped with an interclavicular angle of 59 degrees. It has an elongate hypocleidium and U-shaped shaft cross section. The sternum is basically wider than long and semicircular in front. Two elongate posterolateral processes are expanded distally and anteriorly separated from the sternal body by notches. Posteriorly, there is an elongate medial process and two smaller processes between it and the posterolateral processes. A carina is developed posteriorly. At least four pairs of sternal ribs are present and decrease in length posteriorly.
The humerus resembles enantiornithines in general outline- sigmoid with a long low deltopectoral crest, strongly posteriorly projected bicipital crest and distally projected internal condyle. Compared to Enantiornis , the deltopectoral crest is longer, internal condyle less distally projected, shaft more sigmoid, bicipital crest narrower and head more developed internally. The humerofemoral ratio is 1.64, while the radius is 89% of humeral length. The ulna is bowed, while the radius is straight and 63% as wide. The carpus consists of a small radiale, large triangular ulnare and semilunate unfused to the metacarpus. The metacarpus is unfused, with the third metacarpal extending past the second. It is about half as wide as the second and bowed laterally. The first digit extends past metacarpal II and features a mid-sized ungual. On the second digit, phalanx II-1 is slightly longer than II-2 and the ungual is larger than that on digit I. Only two phalanges are present in the third digit, the second which is tiny and triangular, but apparently not an ungual.
An ilium preserves a rounded preacetabular process and a short pointed postacetabular process. The pubis is cranially convex, with a pubic foot twice shaft width. The ischium is about 60% of pubic length, with a reduced obturator process, straight shaft and well developed posterodorsal process.
No femoral details are observable, but the tibia has a strong fibular crest. It is unfused with the astragalocalcaneum, but combined their length is only 7% longer than the femur. The fibula is reduced, tapering distally so that it does not contact the calcaneum. The tarsometatarsus is fused proximally, as are the distal tarsals. Metatarsal I is curved, with a reversed first digit. Phalanx I-1 is elongate with a moderately curved ungual. The metatarsals decrease in length medially, IV is slightly narrower than II. The proximal phalanges are preserved, but no details are available.
Contour feathers are preserved around the cervical, pectoral and pelvic area. The flight feathers attached to the ulna appear very short, but impressions of the distal sections may be present. The extremely long arms and advanced flight adaptations show this taxon was volant in any case.
Zhang et al. refer the genus to a new family and order (Longipterygidae, Longipterygiformes) within the Enantiornithes. They assigned it to the latter clade based on- elongate hypocleidium; \\\"sternum similar to that of Cathayornis and Eoalulavis\\\"; metacarpal III longer than metacarpal II. The first and third are found in the more basal form Protopteryx, while the second is confusing. Eoalulavis has a very derived sternum that is narrow without lateral processes and has a greatly expanded posteromedial process. It is not similar to Cathayornis or Longipteryx in any regard. Longipteryx\\\'s sternum is roughly similar to Cathayornis , like a cross between it and Protopteryx. No sternal synapomorphies are apparent that would unite Longipteryx with enantiornithines.
To determine Longipteryx\\\'s phylogenetic position, it was added to my basal pygostylian character matrix of 36 characters. Included taxa are Confuciusornithidae, Protopteryx, Longipteryx, Jibeinia, Enantiornithes and Euornithes. One most parsimonious tree (54 steps, CI .81) was found-
When Liaoxiornis, \\\"Archaeoraptor\\\" or Eoenantiornis were added, the first two grouped with Jibeinia + Ornithothoraces, while the second was an ornithothoracine. They did not affect the topology.
Longipteryx is more derived than confuciusornithids based on- strut-like coracoid; interclavicular angle of furcula 70 degrees or less; long hypocleidium; furcula laterally excavated; elongate posterolateral sternal processes; ulna subequal or longer than humerus; less than four phalanges on manual digit III; reduced manual unguals. It is more derived than Protopteryx based on- more than seven sacral vertebrae; anterior sternal edges at less than a 120 degree angle; narrow posteromedial sternal process; noticeable processes medial to posterolateral sternal processes; manual phalanx II-2 shorter than phalanx II-1; metatarsal V absent.
It is less derived than Jibeinia based on- gastralia present; posterior sternal processes medial to posterolateral sternal processes not pointed; manual digit I longer than metacarpal II. In addition, it lacks the following ornithothoracine characters- scapula tapered distally; interclavicular angle of furcula 50 degrees or less; less than two phalanges on manual digit III. I feel the evidence is good that Longipteryx is a non-ornithothoracine pygostylian phylogenetically between Protopteryx and Jibeinia.
Zhang, F., Zhou, Z., Hou, L., and Gu, G. 2001. Early diversification of birds: Evidence from a new opposite bird. Chinese Science Bulletin 46(11): 945-950.