Dendrocygna nazensis, Houde et al., 2023
|
publication ID |
https://doi.org/ 10.26879/1301 |
|
publication LSID |
lsid:zoobank.org:pub:7C46BBEC-EEDC-4EF1-B821-9284F9BA8408 |
|
persistent identifier |
https://treatment.plazi.org/id/03AF87E9-FF9C-2F35-FC1A-FE201609CFC6 |
|
treatment provided by |
Felipe |
|
scientific name |
Dendrocygna nazensis |
| status |
|
Danielsavis nazensis Houde et al., 2023
Holotype. NMS.Z.2021.40.1 ( Figure 1A View FIGURE 1 ; partial skeleton including tip of upper beak, left and right mandibular rami, both quadrates and pterygoids, partial hyoid apparatus, at least 18 presacral vertebrae, cranial portion of sternum, partial furcula, right and partial left coracoid, cranial portions of both scapulae, left and distal end of right humerus, both radii, left ulna, ossa carpalia and wing phalanges, right and proximal portion of left carpometacarpus, distal end of right femur, proximal end of left and distal end of right tibiotarsus, right and distal end of left tarsometatarsus, pedal phalanges).
Referred specimens. NMS.Z.2021.40.2 ( Figure 1B View FIGURE 1 ; partial skeleton including partial skull and mandible, both quadrates, partial hyoid apparatus, six cervical vertebrae, cranial portion of sternum, partial furcula, right coracoid, cranial portion of right scapula, proximal end of right humerus); NMS.Z.2021.40.3 ( Figure 1C View FIGURE 1 ; partial skeleton including two cervical, two thoracic, and two caudal vertebrae, partial sternum, distal portion of left ulna, left radius, proximal end of right carpometacarpus, distal end of left femur, proximal and distal ends of right tarsometatarsus, and pedal phalanges); NMS.Z.2021.40.6 ( Figure 1D View FIGURE 1 ; left tarsometatarsus, pedal phalanges).
Remarks. Houde et al. (2023) only considered the holotype to be definitely referable to Danielsavis nazensis . NMS.Z.2021.40.2 is slightly larger than the holotype, and according to Houde et al. (2023: 32), the specimen differs from the holotype “because in lateral view the orbital process of the quadrate is narrower and the dorsal margin of the quadrate between it and the otic process is more uniformly curved. The premaxilla is slightly longer and narrower than that of Danielsavis nazensis (…). The tubercle of the external head of the AME [= (musculus) adductor mandibulae externus], pars articularis is positioned closer to the dorsal margin of the coronoid region”. Unlike in the holotype (NMS.Z.2021.40.1), the quadrate of NMS.Z.2021.40.2 furthermore exhibits a well-defined albeit small condylus pterygoideus and the scapula of the holotype is proportionally longer and narrower than in NMS.Z.2021.40.2. Some of these differences may be due to the somewhat larger size of NMS.Z.2021.40.2, and we consider it possible that they are due to intraspecific variation.
With regard to NMS.Z.2021.40.3, Houde et al. (2023: 34) noted that the “alular metacarpal of the carpometacarpus is extremely short proximodistally and positioned proximally, such that the distal limits of the alular process and the pisiform process are approximately equal, unlike the holotype of Danielsavis nazensis ”. However, the os metacarpale alulare of NMS.Z.2021.40.3 is broken and was glued together by the collector, so that this difference is likely to be an artefact of an erroneous restoration of the bone .
Emended description. In the following, we focus on features that were not already mentioned by Houde et al. (2023). The upper beak of Danielsavis ( Figure 2A‒D View FIGURE 2 ) has a distinctive shape in that its lateral margins run in parallel and in that the tip is not deflected and does not form a hook. Even though it resembles the upper beak of Anhima cornuta ( Anhimidae ) in its outline, the straight tomia distinguish it from crown group Anhimidae . The beak of Anachronornis has a more spatulate shape with a broadly rounded tip; the nostrils are proportionally longer than in Danielsavis. Mayr (2022) considered the beak of Danielsavis to be similar to that of Asteriornis from the Late Cretaceous of Belgium ( Field et al., 2020), but in spite of a similar outline it is proportionally shorter; the interorbital section of the neurocranium is wider than in Asteriornis and Anachronornis. As noted by Houde et al. (2023), the lacrimals appear to be co-ossified with the frontals; on the right side of the skull, there is a small foramen that pierces the skull roof in the presumed area of fusion ( Figure 1B View FIGURE 1 ), but it is uncertain whether this is a true osteological feature or the result of damage (a similar foramen is also present in some extant anseriforms with co-ossified lacrimals, such as Cairina moschata ).
Specimen NMS.Z.2021.40.2 preserves the basicranial area and substantial portions of both palatine bones ( Figure 2E‒G View FIGURE 2 ), which were not described by Houde et al. (2023). The right basipterygoid process is visible, being sessile and of ovate shape as in extant galloanserines. The morphology of the palatines is intermediate between that of crown group Galliformes and crown group Anseriformes . As in Anachronornis and galliforms, but unlike in crown group Anseriformes , the caudal portions of the palatines are not co-ossified. The crista ventralis is low and separates the bone into two portions of subequal width (pars lateralis and lamella dorsalis, pars choanalis palatini sensu Zusi and Livezey, 2006). The pars lateralis is mediolaterally wider than in crown group Galliformes ( Figure 2H View FIGURE 2 ), but as in the latter and unlike in crown group Anseriformes ( Figure 2I, J View FIGURE 2 ), the lateral margin of the palatine is evenly curved and does not form a well-defined angulus caudolateralis (the condition in Anachronornis is similar to that of Danielsavis).
The quadrate ( Figure 3A‒H View FIGURE 3 ) was figured by Houde et al. (2023), who noted some galloanserine features of the bone in the differential diagnosis and commented on the presence of a foramen pneumaticum basiorbitale; this foramen is absent or vestigial (some Anhimidae ) in crown group Anseriformes ( Elzanowski and Stidham, 2010) . As in other galloanserine birds, the processus mandibularis is bicondylar and lacks a condylus caudalis. In its proportions and general features, the quadrate of Danielsavis corresponds well to that of Presbyornis , which likewise exhibits a more plesiomorphic quadrate morphology than crown group Anseriformes ( Elzanowski and Stidham, 2010) . The tuberculum subcapitulare is distinct but small. The processus orbitalis is proportionally longer and narrower than in Anachronornis. In NMS.Z.2021.40.1, a well-defined condylus pterygoideus is absent, whereas this condyle is very small in NMS.Z.2021.40.2; a small prominence on the processus orbitalis may represent an articulation facet for the pterygoid. The cotyla quadratojugalis exhibits a facies quadratojugalis ventralis sensu Elzanowski and Stidham (2010).
Both pterygoids are present in the holotype ( Figure 3O‒R View FIGURE 3 ). The bones were not described by Houde et al. (2023) and ‒ except for the shorter processus rostralis ‒ most closely resemble the pterygoid of Nettapterornis (“ Anatalavis ”) oxfordi in overall proportions (compare Figure 3O‒R View FIGURE 3 with Olson, 1999: figure 3). As in the latter species, the facies articularis basipterygoidea is proportionally wider than in crown group Anseriformes ( Figure 3K, L View FIGURE 3 ). The pterygoid of Danielsavis is clearly distinguished from the pterygoid of galliform birds ( Figure 3I, J View FIGURE 3 ), in which the facies articularis basipterygoidei is less protruding and situated near the rostral end of the bone.
The hyoid apparatus ( Figure 3S‒U View FIGURE 3 ), which was likewise not described by Houde et al. (2023), has a wide basihyal, which tapers rostrally and forms lateral wing-like projections. Within extant Galloanseres a similar morphology occurs in the Anseranatidae ( Figure 3X View FIGURE 3 ), whereas the basihyal of the Anhimidae ( Figure 3W View FIGURE 3 ) and Galliformes ( Figure 3V View FIGURE 3 ) is narrow and rod-shaped. A small, subrectangular ossicle is here tentatively identified as the os paraglossum ( Figure 3U View FIGURE 3 ); if this identification is correct, the bone is distinctly smaller than the paraglossum of crown group Anseriformes .
The caudal (articular) end of the mandible ( Figure 2K‒P View FIGURE 2 ) exhibits the characteristic derived morphology of galloanserine birds, in which a rostrocaudal ridge separates two articular surfaces for the quadrate. As in other Galloanseres, a long processus retroarticularis is present, which is completely preserved in the left mandibular ramus of the holotype. The processus retroarticularis of Danielsavis is sharply dorsally angled, by which it differs from Anachronornis ( Figure 2R View FIGURE 2 ). The mandibular rami are dorsoventrally lower than in Asteriornis, Anachronornis , Presbyornis , and all crown group Anseriformes and agree with the mandibular rami of galliform birds in their proportions. This is also true for the short symphysis, which is mediolaterally narrower than the mandibular symphysis of crown group Anseriformes . On the lateral surface of the mandibular ramus there is an elongated, flange-like process that served for the attachment of musculus adductor mandibulae externus (“tubercle of the external head of the AME, pars articularis” sensu Houde et al., 2023: 32). A similar flange is present in the Megapodiidae , but absent in other crown group Galliformes ( Cracidae and Phasianidae ); in crown group Anseriformes it is weakly developed in the Anhimidae and very pronounced in the Anseranatidae and Anatidae .
The holotype includes at least 18 presacral vertebrae or fragments thereof, with this vertebral series being complemented by vertebrae preserved in NMS.Z.2021.40.2 and NMS.Z.2021.40.3. Houde et al. (2023) commented on the morphology of the atlas, which exhibits foramina transversaria ( Figure 4A View FIGURE 4 ); in extant Galloanseres, these foramina occur in the Anseranatidae and Anatidae ( Figure 4C View FIGURE 4 ), whereas they are absent in the Anhimidae ( Figure 4B View FIGURE 4 ) and Galliformes ( Figure 4D View FIGURE 4 ). As further noted by Houde et al. (2023), the thoracic vertebrae bear large pneumatic openings on the lateral surfaces of the corpus ( Figure 4E View FIGURE 4 ); these openings are present in anseriforms but absent in galliforms ( Mayr, 2021). Other vertebrae were not described by Houde et al. (2023). The axis, which is present in NMS.Z.2021.40.2 ( Figure 4E, F View FIGURE 4 ), is proportionally shorter than that of Conflicto and in its shape resembles the axis of Chauna ( Anhimidae ; Figure 4B, G View FIGURE 4 ); it bears a long and ridge-like processus spinosus. In their proportions, the third to fifth cranial vertebrae are more similar to the corresponding vertebrae of crown group Anseriformes than to the wider vertebrae of crown group Galliformes . The third and fourth cervicals ( Figure 4A, J, K View FIGURE 4 ) exhibit a small notch (third) or foramen (fourth) on one side of the corpus, but these are much smaller than the foramina in the corresponding vertebrae of galliforms and some anseriforms. The large processus ventralis of the third vertebra is pierced by foramina ( Figure 4K View FIGURE 4 ). The vertebra that is here identified as the fifth cervical is only preserved in NMS.Z.2021.40.3 ( Figure 4A View FIGURE 4 ); it is much longer than wide and has a caudally tapering corpus; a lateral lamella along its corpus delimits a foramen in the cranial portion of the vertebra. The lateral surfaces of the corpus of some cervical vertebrae bear small, irregular and lamellate projections ( Figure 4E View FIGURE 4 ), which are fewer and less pronounced than the barb-like tubercles in the fossils we refer to Perplexicervix (see further below). One of the thoracic vertebrae preserved in NMS.Z.2021.40.3 exhibits ossified tendons attached to the processus spinosus and the zygapophysis caudalis ( Figure 4L View FIGURE 4 ); a long processus ventralis identifies this vertebra as one of the cranial thoracics. The pygostyle is preserved in the holotype and has a craniocaudally wide lamina; the dorsal portion of the lamina pygostyli is broadly rounded.
The coracoid of Danielsavis ( Figure 5A, B View FIGURE 5 ) differs from that of Anachronornis ( Figure 5D View FIGURE 5 ) and other anseriforms ( Figure 5E, F View FIGURE 5 ) in that the crista procoracoidei is more strongly developed, the omal extremity proportionally shorter, and the angle between the medio-omal and latero-omal portions of the processus acrocoracoideus is more obtuse. With regard to the shape of the processus acrocoracoideus, the bone resembles the coracoid of early Paleogene stem group Galliformes ( Figure 5C View FIGURE 5 ). The facies articularis clavicularis does not form a lip-like projection and the impressio ligamenti acrocoracohumeralis is not as marked as in Anachronornis and other anseriforms. The facies articularis humeralis is more laterally facing than in Anachronornis, in which it is more dorsally directed. The foramen nervi supracoracoidei is large. The medial margin of the extremitas sternalis forms a small projection, which is also found in other fossil Galloanseres. The processus lateralis is less drawn in sternolateral direction than in Anachronornis and Nettapterornis ( Figure 5E View FIGURE 5 ). Houde et al. (2023: 29) noted the presence of potential pneumatic foramina on the dorsal surface of the extremitas sternalis of NMS.Z.2021.40.1, but we consider these foramina to more likely be artefacts of damage to the bones.
Unlike in galliform birds, the extremitas omalis of the furcula ( Figure 5G View FIGURE 5 ) forms a well-developed processus acromialis (in galliform birds the omal extremity is widened and has a straight end). The apophysis furculae is small. The scapus claviculae of NMS.Z.2021.40.2 exhibits an unusual mediolateral widening in its omal portion ( Figure 1B View FIGURE 1 ), which may represent a pathological feature. The scapula has a long and narrow acromion, similar to that of the putative presbyornithid Wilaru tedfordi from the late Oligocene of Australia ( De Pietri et al., 2016: figure 1g).
The humerus ( Figure 5L, M View FIGURE 5 ) is notably stouter than that of Anachronornis and anseriforms ( Figure 5N, O View FIGURE 5 ) and has a proportionally wider proximal end. The tuberculum dorsale is proximodistally longer than it is mediolaterally wide and is proportionally longer than in Anachronornis and crown group anseriforms. On the distal end of the bone, the processus flexorius is more developed than in Anachronornis and other anseriforms.
The proximal end of the ulna ( Figure 5R View FIGURE 5 ) closely agrees with that of galliform birds ( Figure 5S View FIGURE 5 ), and as in the latter the cotyla dorsalis reaches much farther distally than the cotyla ventralis. The carpometacarpus ( Figure 5U, V View FIGURE 5 ) has a proportionally wider spatium intermetacarpale than the carpometacarpus of Anachronornis ( Figure 5X View FIGURE 5 ) and other anseriforms. Furthermore, unlike in Anachronornis, Nettapterornis ( Figure 5W View FIGURE 5 ) and crown group Anseriformes , the trochlea carpalis is not proximocaudally projected.
The phalanx proximalis digiti majoris exhibits a processus internus indicis. The os carpi radiale ( Figure 5Y, Z View FIGURE 5 ) corresponds to that of anseriforms ( Figure 5 View FIGURE 5 AA), whereas the corresponding ossicle of crown group galliforms has a disparate, autapomorphic shape ( Figure 5 View FIGURE 5 BB).
The tibiotarsus ( Figure 6A View FIGURE 6 ) differs from that of crown group anseriforms in that the sulcus extensorius is medially rather than centrally situated. The condylus medialis is much narrower than the condylus lateralis. Only a fragment of the proximal end is preserved in the holotype, which shows cristae cnemiales of average size.
The tarsometatarsus ( Figure 6F‒J View FIGURE 6 ) is proportionally shorter than the tarsometatarsus of the Anhimidae . Unlike in crown group Anseriformes , the plantar articular surface of the trochlea metatarsi III is asymmetrical, with a more proximal lateral rim ( Figure 6J View FIGURE 6 ). In contrast to Anachronornis ( Figure 6N View FIGURE 6 ), the trochlea metatarsi II is not much shorter than the trochlea metatarsi IV. The hypotarsus was described by Houde et al. (2023: 30) as showing “a single deep sulcus”, but in specimen NMS.Z.2021.40.3 there are two shallow sulci, presumably for the tendons of m. flexor digitorum longus and m. flexor hallucis longus ( Figure 6E View FIGURE 6 ). In proximal view the hypotarsus corresponds to that of Presbyornis ( De Pietri et al., 2016: figure 2d').
The os metatarsale I is characterised by a deep incision in the distal portion of the trochlea. The pedal phalanges ( Figure 6K View FIGURE 6 ) correspond to those of galliform birds in their proportions, and especially those of the fourth toe are much shorter than the corresponding phalanges of most anseriform birds (exceptions are the taxa Cnemiornis and Cereopsis , in which equally short phalanges occur), with the third phalanx of the fourth toe being particularly short. Houde et al. (2023) hypothesised that the longest phalanx represented in the phalangeal set is from the hallux, but we consider this phalanx to be the first phalanx of the second toe. The first phalanx of the hallux, which is identified by the asymmetrical shape of its proximal end, is rather shorter.
| NMS |
National Museum of Scotland - Natural Sciences |
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
|
Kingdom |
|
|
Phylum |
|
|
Class |
|
|
Order |
|
|
Family |
|
|
Genus |