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RE: Dingavis, new ornithuromorph bird from Lower Cretaceous of China



Extremely good find!  As for the differences...

- Dingavis is from Sihedang, which as I note in my Iteravis entry- "Zhou et al. 
(2014) believed the Sihedang locality which these 
  specimens derive from to be in the Yixian Formation, whereas Liu et al. 
(2014) 
  believed it to be in the overlying Jiufotang Formation. Zhou et al. cite 
undescribed 
  turtles and a caudipterid as being found in the locality, though both are 
known 
  from both formations (as Similicaudipteryx has been referred to 
Caudipteridae, 
  though it is near certainly more basal). The pterosaurs Guidraco and 
  Ikrandraco are also from Sihedang however, referred to the Jiufotang 
  Formation in both descriptions. As Ikrandraco is also known from another 
  Jiufotang locality (Lamadong), the Jiufotang Formation is favored here as the 
  stratigraphic placement of Iteravis."  Dingavis being the same as Juehuaornis 
(from Lingyuan) would be further evidence Sihedang is in the Jiufotang 
Formation.
- Agreed regarding manual phalanx III-2.  Dingavis is pretty terribly preserved 
(note only one proximal carpal is preserved per side), so I wouldn't be 
surprised if tiny phalanges went missing.
- For the hooked bill, note that in Dingavis the predentary ("mandibular 
symphysis" of the authors) is disarticulated so that figure 3A would appear to 
have a frigatebird-style hook if you didn't know better.  Could easily be what 
happened with Juehuaornis.
- Much as with phalanx III-2, Dingavis' poor preservation could easily hide 
tiny teeth.  So I agree there as well.

In total, I think you're correct and that the two are synonymous.  Between this 
and Chiappeavis, O'Connor's taxa are dropping like flies...

Mickey Mortimer

----------------------------------------
> Date: Wed, 13 Jan 2016 00:40:44 +0800
> From: albertonykus@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Dingavis, new ornithuromorph bird from Lower Cretaceous of China
>
> Apologies to those who received this message already. Resending it
> because, based on the DML live feed, I don't think it ma
.
>
> Could Dingavis be the same as Juehuaornis? I have not done all the
> legwork necessary to evaluate this question, but considering that the
> description of Dingavis does not mention Juehuaornis despite both
> being long-snouted Early Cretaceous euornithines, it seems worthy of
> exploration.
>
> Confounding matters further, the description of Juehuaornis is brief,
> provides no exact measurements of skeletal elements, and is
> illustrated with only a single low-res photo of the holotype slab and
> counterslab. Regardless, there are some suspicious similarities based
> on the information available. All of this is based on a comparatively
> quick gleaning of the two description papers and is by no means
> intended to be a complete overview.
>
> First of all, the diagnoses of each taxon compared to the
> characteristics seen the other.
>
> The diagnosis of Dingavis, compared to Juehuaornis:
> -Rostrum forms 63 -65% of total skull length: Rostrum is ~70% of total
> skull length in Juehuaornis
> -Jugal process of lacrimal caudolaterally excavated: Not described in
> Juehuaornis
> -Both upper and lower jaws edentulous: Maxillary and dentary teeth
> present in Juehuaornis
> -Length of carpometacarpus + major digit exceeds humeral length by
> 25%: From quick-and-dirty measurements taken from the photo in ImageJ,
> this ratio is around ~24% in Juehuaornis
> -Short alular metacarpal (13.7% of major metacarpal): Alular
> metacarpal said to be less than 20% the length of the major metacarpal
> in Juehuaornis
> -Tarsometatarsus with small but sharp medial and lateral plantar
> crests, plantar surface not excavated: Not described in Juehuaornis
> -Metatarsal II much shorter than metatarsal IV: Metatarsal II is
> shorter than metatarsals III and IV in Juehuaornis, by how much
> unreported
> -Metatarsal II and IV trochlea plantarly displaced: Not described in 
> Juehuaornis
> -Metatarsal II trochlea strongly angled craniomedially: Not described
> in Juehuaornis
>
> The diagnosis of Juehuaornis, compared to Dingavis:
> -Foreli
> ulna + carpometacarpus length in Dingavis is 124.2 and 132.9 mm and
> preserved femur + tibiotarsus + tarsometatarsus length is132.9 and
> 132.1 mm
> -Rostrum forms ~70% of total skull length: 63-65% in Dingavis
> -Premaxilla hooked and extends beyond mandible: Not seen in Dingavis
> -Anterior of dentary straight: Present in Dingavis
> -Teeth only present in maxilla and dentary: Edentulous in Dingavis
>
> The main differences appear to be the presence of teeth and a hooked
> bill in Juehuaornis. We'll get to that.
>
> Other similarities shared between the two:
> -Femur ~65% the length of the tibiotarsus
> -Ulna and humerus almost equal in length
> -Pedal claws short and barely curved
> -Phalanx 2 on manual digit II dramatically thinner than phalanx 1,
> longer than phalanx 1 but shorter than phalanx 1 on manual digit I
> -Moderate extensor tubercle on manual digit I
> -“Small pubic boot” reported in Juehuaornis; distal pubes said to be
> expanded in Dingavis despite lacking a "distinct" pubic boot
>
> Differences:
> -Juehuaornis is from the Jiufotang Formation while Dingavis is from
> the Yixian. The two formations are already known to have shared some
> fauna, so this is not particularly remarkable.
> -Two phalanges are present on manual digit III in Juehuaornis, whereas
> Dingavis has only one (suggested to be a fusion of the first and
> second phalanges). However, the second phalanx on Juehuaornis is said
> to be highly reduced and would be potentially easy to lose postmortem,
> or perhaps be present in differing degrees of fusion between
> individuals.
> -The "hooked bill" in Juehuaornis is barely visible from the photos
> provided. Given the disarticulated nature of the Dingavis skull, it
> would not surprise me if this feature was distorted or lost through
> taphonomy.
> -And the biggie: the teeth. The maxillary teeth of Juehuaornis are
> reportedly not visible in lateral view and were only identified
> through breakage in the specimen. In fact, due to the poor
> preservation of the skull, the describers 

> the possibility of maxillary teeth. The dentary teeth of Juehuaornis
> are not described as being similarly challenging to find (though
> small) and are said to be numerous. If truly absent in Dingavis, these
> would appear to be the primary point of differentiation between them,
> but, if the two are synonymous, this would not be the first time a
> Mesozoic euornithine was mistaken to be wholly or partially toothless
> in the absence of better-preserved skull material (cf. Hongshanornis).
>
>
> On Tue, Jan 12, 2016 at 1:52 PM, Ben Creisler <bcreisler@gmail.com> wrote:
>> Ben Creisler
>> bcreisler@gmail.com
>>
>>
>> A new paper:
>>
>>
>>
>> Jingmai K. O'Connor, Min Wang & Han Hu (2016)
>> A new ornithuromorph (Aves) with an elongate rostrum from the Jehol
>> Biota, and the early evolution of rostralization in birds.
>> Journal of Systematic Palaeontology (advance online publication)
>> DOI:10.1080/14772019.2015.1129518
>> http://www.tandfonline.com/doi/full/10.1080/14772019.2015.1129518
>>
>>
>> A new species of Early Cretaceous ornithuromorph with an elongate
>> rostrum is described from the Sihedang locality of the Lower
>> Cretaceous Yixian Formation in north-eastern China. Like the
>> longipterygid enantiornithines, rostral elongation in Dingavis
>> longimaxilla gen. et sp. nov. is achieved primarily through the
>> maxilla, whereas neornithines elongate the premaxilla and
>> rostralization is far more extreme than observed in early birds.
>> Notably, in the rostrum of Xinghaiornis, the most ‘longirostrine’
>> Early Cretaceous ornithuromorph, the premaxilla and maxilla contribute
>> to the rostrum equally. These lineages together highlight the
>> diversity of configurations in which early birds experimented with
>> rostralization of the skull. The 65% upper limit in rostral
>> proportions of Early Cretaceous taxa with elongate maxillae and the
>> fact that this morphology was abandoned in more derived taxa suggests
>> that in Aves this skull configuration provided less structural
>> stability.
>>
>> http://
7118833A