Comparative Anatomy of Mu50phagidae (Turacos)

Comparative Anatomy of MU50phagidae (Turacos) by Georgann B. Johnston Sacramento, CA Introduction proVides the red colored feathers in he 20 species which comprise species of the first two genera. Both the avian order Musophagidae' pigments contain copper and spectral (commonly called turacos) data demonstrates that the former is have a number of physical and likely an oxidized version of the latter. anatomical characteristics that set them swered and many generalizations sus (Dyck, 1992) In fact, the two pigments apaI1 from many other birds. While pect in light of new information about are intermingled within individual uniformity among the 20 species is not these species' ecology including feathers in the breast patches and crests complete, ceI1ain generalizations can behavior and diet. of some species and turacoverdin be made. One ofthese is that the sexes occurs only in the presence of turacin. are visually indistinguishable in all of Feathers Other species outside the the species save C. Jeucogaster, in Probably the most distinguishing fea Musophagidae order have turacoverdin which the males have a black beak ture of these birds are two unique pig pigment, including Ithaginis (pheasant) and the females a green beak. ments deposited in their feather keratin. and Rollolus (paI1ridge), both members Unfortunately, most of the literature One, turacoverdin, is a green pigment of the Galliformes. An additional inter regarding the anatomy of these birds found in the rami in all species of esting note is that both pigments are was developed more than 40 years Tauraco and Musophaga, and in soluble in a weak base - which may ago, leaving many questions unan- Corythaeola cristata. 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Internally, a single unifying factor is points to a possible evolutionary rela Another uncommon feature of that all species lack a vomer. (Sibley & tionship between turacos and the these birds is that the feathers of the Ahlquist, 1990) Additionally, the pala hoatzin. The hoatzin is noted for being head and breast of most species are tine processes arise from the more an herbivore that has a crop, which deficient in barbules so that they seem proximal end of the maxillary bone acts as a glandular muscular stomach hairy or have a "down-like texture." and the distal ends of the uncinate used to grind up tough leaves. Thus, a (Moreau, 1938; Moreau, 1958) These bone end in a sharp curve where they reexamination of the digestive anato feathers make up the characteristic meet the outer rim of the palatine. my ofthe Great Blue might be in order erectile "crests" found on all but three (Lowe, 1943) Moreover, the quadrate to see if its foregut differs from other ofthe species. In addition, the contour bone in turacos is pneumatized, one of turacos in conformity with its variant feathers have an aftershaft. (Sibley & the facts that earlier taxonomists relied diet. Likewise, the dietary research Ahlquist, 1990) upon to distinguish these birds from raises the additional question of The wing to tail ratios are uniform cuckoos that have a solid quadrate. whether the Great Blue actually lacks a across the species, with the wing Finally, the tongue is short and thick ceca - since that organ is often length at four-fifths of the tail length. and of a triangular shape, consistent involved in the fennentation-digestion The wings are rounded with the sec with the tongue shape found in other of plant material. ondaries usually a bit shorter than the frugivorous birds. primaries. Also, some of the primaries Skeleton are slotted, probably related to the Digestive System The lack of a furcula is probably the short, slow flight patterns used by Turacos have no crop but do have most significant skeletal feature of these birds. (Moreau, 1958) None of an exceptionally large and well devel these birds. (Sibley & Ahlquist, 1990) the species have eyelashes but all of oped proventriculus, with walls twice This is consistent with the fact that they them do have a tufted, bilobed uropy as thick as those of the gizzard. The are "strictly arboreal, but poor flyers, gial gland. (Lowe, 1943) gizzard, in tum, has only a thin mus moving from canopy to canopy with cular structure with no horny cuticle or bursts of flapping and unstable-look Feet koilin lining its interior. Additionally, ing gliding." (Fry, et al., 1988) With These birds are defined as having turacos lack a caeca. These anatomical slight variation, all species have 15 cer semi-zygodactyl feet with the fourth features are consistent with the fact vical vertebrae, 19 presacral vertebrae toe being reversible and not perma that turacos are primarily frugivores, and five dorsal vertebrae. nently directed backwards. A typical though they have been known to eat With respect to the skull, character resting position will find the outer toe insects and snails, particularly when istics of note include relatively huge at approximate right angles to the they are feeding young in the nest. lacrymals that connect with the frontal main axis of the foot, but it can be (Fry, et al., 1988) The major exception bones and a large horizontal and back moved further back or directed for to this diet is seen in the Great Blue wardly projecting process of bone that ward, depending upon the bird's Turaco C. cristata which ingests a sig is deeply grooved for the passage of perching needs. Additionally, the nificant number of leaves, algae, and the nasal ducts. (Lowe, 1943) Turacos claws are short and abruptly curved. rootless floating plants as part of its are classified as desmognathous birds (Moreau, 1938) Some researchers have diet. (Sun, et al., 1997) as stated above, there is not a com reported that nestlings have a short Since so little has been published plete "shelf' between the nasal and (approximately Imm) wing-claw but regarding the digestive systems of the oral cavities. this seems to vary from species to turacos it is difficult to make accurate It is interesting to note that studies species and even among individuals generalizations regarding this portion of the fossil record demonstrates cer within a species, and because of this it of their anatomy. Two studies regard tain similarities between the "basal cannot be said with certainty that it is ing intestinal parasites have been land bird assemblage" and turacos, tin a defining anatomical feature. undertaken, primarily for the purpose namous, gallifonnes, cuckoos, and (Moreau, 1958; Fry, et al., 1988) of determining the phylogenetic rela hoatzins. (Olson, 1985; Houde, 1988) tionship ofthese birds to other species, This conclusion is based, primarily, on Beak & Head but these studies do not describe the the well-defined terminal iliac process All turacos have short strong beaks anatomy in any detail. (Clay, 1947; of the modem birds resembling the with curved culmen. In some species Bennett, 1993) lithornithid pelvis. the culmen is ridged (T bannermani, As an aside, with the recent confir An observation based on ecology leucolophus, and macrorhynchus) and mation by Sun and his associates that alone seems to have been proved cor in others curves back into a frontal plate a significant portion of the diet of C. rect: all of these birds inhabit an area (M. rossae and violacea). The nostrils cristata is leaves and related plant mat surrounding the "equatorial rain belt" are located on the beak but vary in ter, it would be interesting to pursue which has been "remarkably stable in shape and position. Some species have the comparative anatomy of the diges shape and extension from early slit-shaped nares while others have cir tive system of the turacos generally Tertiary times - that is, for long as cles; in many species the nostrils are and the Great Blue in particular. Musophagidae are likely to have been covered with feathers. (Moreau, 1958) As stated below, recent research a distinct family." (Moreau, 1958) 44 July/August 1999 Muscles this order need to be refined and more Yeterinarians The muscles of the wings and accurately delineated, particularly in Commercial embers brea t are "relative to most other birds, light of recent discoveries with respect feehly developed, and are long, thin to ecology, diet, and DNA structure. Bobbie Faust, DVM and narrow slips." (Lowe, 1943) The With many of the turaco species listed Faust Animal Hospital, Al, 602-482-2191 pelvic muscles include the caud as endangered or threatened by CITE , Ross Babcock, DVM Palo Verde Animal Hospital, Al, 602-944-9661 ofemoralis, iliofemoralis, semi-tendi new information about their anatomy Hillary Frank, DVM, nosus, accessory semi-tendinosus, and physiology, which could con North Central Animal Hospital, Al, 602-395-9773 iliofemoralis externus, iliacus plantaris tribute to succes ful captive breeding and the popliteus.

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