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David Marjanovic asked-
Is *Liaoxiornis* diagnostic when its ontogenetic age is taken into account?
I doubt it, but I haven't examined the question since my old DML post.
How did you code the ontogeny-dependent characters of *Iberomesornis* --
They seem to be mostly misinterpretations (Sereno, 2000). The exceptions
are the concave lateral sternal margin and proximally convex humeral head,
both of which are also plesiomorphic for enantiornithines.
Conveniently, I had a section written up on ontogeny...
Several included specimens (Liaoxiornis, Dahlingheornis, IVPP V14238 (the
Yixian embryo), LP-4450-IEI (the Catalan nestling), GMV 2158 and GMV 2159
(two Yixian specimens examined by Chiappe 2002)) are obviously juvenile, and
therefore differ from adult specimens in a number of characters (no sternal
keel or lateral processes, lack of fusion, etc.). I initially coded these
as unknown then ran the analysis to find the juveniles still claded
together. After examining the list of apomorphies for their node, I was
able to identify several other probable juvenile characters. Once these
were all coded as unknown for the juveniles, they began intermingling with
adult specimens. The juvenile characters identified were-
1.(?) external naris smaller than antorbital fenestra (LP-4450-IEI,
Liaoxiornis, GMV 2158, IVPP V14238)
2.atlantal hemiarches fusion absent (LP-4450-IEI)
3.less sacral vertebrae (6 in Liaoxiornis, GMV 2158; 6-7 in IVPP V14238; no
4.(?) caudal transverse processes shorter (Liaoxiornis, GMV 2159)
5.pygostyle absent (Dalingheornis, IVPP V14238; no in Liaoxiornis, GMV 2159)
6.sternum reduced in size (Liaoxiornis, GMV 2158, GMV 2159)
7.sternal keel absent (Liaoxiornis, GMV 2159)
8.lateral sternal process absent (Liaoxiornis, GMV 2158, GMV 2159; no in
9.(?) lateral sternal process unexpanded (Dalingheornis)
10.medial sternal process absent (Liaoxiornis, GMV 2158, GMV 2159)
11.higher interclavicular angle (Dalingheornis especially; Liaoxiornis, GMV
2158, GMV 2159; no in LP-4450-IEI, IVPP V14238)
12.(?) lateral coracoid not convex (Dalingheornis, LP-4450-IEI, Liaoxiornis,
GMV 2158, GMV 2159, IVPP V14238)
13.capital groove absent (Dalingheornis; no in LP-4450-IEI)
14.humeral head concave in middle (Dalingheornis, Liaoxiornis, GMV 2158, GMV
2159; uncertain in LP-4450-IEI)
15.(?) humeral pneumotricipital fossa absent (LP-4450-IEI, GMV 2158)
16.(?) deltopectoral crest reduced in depth (Dalingheornis, Liaoxiornis, GMV
2158, GMV 2159, IVPP V14238)
17.humeral distal condyles undeveloped (Dalingheornis?, Liaoxiornis?, GMV
2159, IVPP V14238; no in LP-4450-IEI)
18.semilunate ridge on distal ulna absent (Dalingheornis, Liaoxiornis, GMV
2158, GMV 2159; no in LP-4450-IEI)
19.(?) manus longer than humerus (IVPP V14238; equivocal in Dalingheornis;
no in LP-4450-IEI, GMV 2159)
20.carpometacarpus fusion absent (Dalingheornis, Liaoxiornis, GMV 2158, GMV
2159; no in LP-4450-IEI)
21.pelvic fusion absent (GMV 2158)
22.(?) pubic boot absent (GMV 2158, IVPP V14238)
23.(?) ischiopubic ratio <66% (Dalingheornis, GMV 2158)
24.cnemial crest absent (Dalingheornis, GMV 2158)
25.tibiotarsal fusion absent (Dalingheornis, GMV 2158, GMV 2159; no in
26.astragalus fused to calcaneum
27.tarsometatarsal fusion absent (GMV 2158; GMV 2159; IVPP V14238; no in
28.metatarsal trochlea undeveloped (Dalingheornis)
It became obvious that the supposedly primitive characters of a few taxa
(Jibeinia, Protopteryx, Longipteryx) were also potential juvenile
characters. This isn't necessarily true however, as many of these
characters' juvenile states are primitive for Enantiornithes and more
inclusive clades. I created a new ontogeny matrix with these 28 characters,
and included the juveniles, three taxa mentioned above, as well as some
others which have apparent juvenile characters (Gobipteryx "N. valifanovi"
specimen, Hebeiornis, "Cathayornis" caudatus). Iberomesornis has been
suggested to be juvenile in the past, so was also included. Sinornis was
used as an example of an adult enantiornithine. Running this created an
'ontogram', as Carr (2005) and Tykoski (2005) have done for tyrannosaurids
and coelophysoids respectively. The embryo was used as an outgroup. There
was some homoplasy, but the resulting ontogram was-
It should be read as a progression of age, with more "derived" taxa being
older. Interestingly, LP-4450-IEI groups close to the adult. It does
possess juvenile bone texture, so we know it wasn't fully grown. The taxa
'less derived' than it on the tree should be examined for this texture too.
The transformations occuring at each age level are as follows-
Specimens older than IVPP V14238-
- manus shorter than humerus (not in Protopteryx, Longipteryx).
Specimens older than Liaoxiornis, GMV 2158, GMV 2159-
- eight sacral vertebrae (not in Protopteryx); lateral sternal processes
ossify; **metatarsals fuse.
Specimens older than Dalingheornis
- **pygostyle fused (also in Liaoxiornis, GMV 2159; not in "Cathayornis"
caudatus); **sternum enlarges; medial sternal processes ossify (not in
Protopteryx); pneumotricipital fossa; semilunate ridge on distal ulna.
Specimens older than Jibeinia-
- naris longer than aof (not in Gobipteryx); sternal keel; capital groove;
**humeral distal condyles develop; pubic boot (not in Gobipteryx); ischium
Specimens older than Protopteryx, Longipteryx-
- low interclavicular angle (also in IVPP V14238); lateral coracoid convex
(also in Jibeinia; not in LP-4450-IEI, Iberomesornis); humerus concave in
middle? (also in Longipteryx; not in Iberomesornis); **carpometacarpus
fused; cnemial crest (not in "Cathayornis" caudatus); **astragalus fused to
calcaneum; **metatarsal trochlea developed.
Specimens older than Gobipteryx, Hebeiornis-
- lateral sternal processes expanded distally (also in Longipteryx); pelvis
fused; **proximal tarsals fused to tibia.
Jibeinia, Protopteryx and Longipteryx were then recoded with the characters
they possess juvenile morphology for coded as unknown. These alternative
"adult" versions were run separately and together to determine their effect
on the taxon's placement. Characters marked by asterisks are those in which
Confuciusornis and Sapeornis possess the derived/adult state, making it
unlikely (though not impossible) that a basal enantiornithine would have the
basal state due to phylogeny instead of ontogeny. When taxa have
juvenile/basal states which overall younger specimens lack, it could mean
they kept the juvenile/basal states into adulthood. For instance,
Protopteryx and Longipteryx may have had long manus even as adults, while
adult Gobipteryx may have had small external nares and no pubic boot.
Protopteryx and Longipteryx ended up having the same position whether
juvenile states were coded for them or not, but Jibeinia was quite a bit
more derived if assumed to be a juvenile. As Jibeinia was found to be
younger in my test above, perhaps that marks the point in life where
enantiornithine taxa can be safely analyzed without the need to adjust their
codings for age?