Pseudocrypturus: close to the base of all living birds

Pseudocrypturus cercanaxius
(Houde 1988; Early Eocene) was originally considered a northern hemisphere ancestor to ratites (like the ostrich, Struthio). Today primitive flightless birds are chiefly restricted to the southern hemisphere. But note #11 below.

Figure 1. The world at the K-T boundary, 65 mya and the distribution of Paleocene birds.

Figure 1. The world at the K-T boundary, 65 mya and the distribution of Paleocene birds.

Then again,
it could be that early birds did start in the South at the K-T boundary, finding refuge near the antipodes from the Yucatan crater site (like China), and had migrated back around the world and back to the North during the Paleocene (66–56 mya). We looked at the record of Paleocene birds earlier here, (Fig. 1) but we didn’t talk about what sort of birds these were. Here they are again with a few more details.

  1. WaimanuNew Zealand sphenisciform close to penguins
  2. AustralornisNew Zealand precursor to living sea bird families
  3. QianshanornisChina cariamiform close to Cariama
  4. QinornisChina closer to Mesozoic birds (divisions still visible in the metatarsus)
  5. LithornisN. America lithornithiform close to Pseudocrypturus
  6. OgygoptynxN. America strigiform (owl)
  7. NovacaesarealaN. America procellariform? (sea bird) close to Torotix
  8. FissuravisEurope lithornithiform close to Pseudocrypturus
  9. BerruornisEurope strigiform close to Bubo, the owl
  10. Gastornis Europe giant anseriform (LRT nests it with the herbivore hoatzin, Opisthocomus)
  11. Remiornis Europe ratite close to Rhea
  12. Lithoptila N. Africa prophaethontid (sea bird) close to Phaethon
  13. Paleopsilopterus – S. America giant cariamiform close to Phorusrhacos
  14. ItaboravisS. America cariamiform close to Cariama
  15. DiogenornisS. America ratite close to Rhea
  16. This list is not complete

Ornithologists generally agree
that most major bird families diversified or were present in the Paleocene. Given the variety of birds already known, though scarce, this appears to be valid.

Since ratites are basal to extant birds,
and Pseudocrypturus is basal to ratites (paleognaths), Pseudocrypturus may be similar to the ancestor of all extant birds, perhaps a ‘living fossil’ in the early Eocene. Given its basal position in the LRT, perhaps something very much like it was one of the few survivors of the K-T extinction event.

Figure 1. My introduction to Pseudocrypturus was as this drawing in Carroll 1988. Here a DGS tracing of the skull is compared to earlier drawings.

Figure 2. My introduction to Pseudocrypturus was as this drawing in Carroll 1988. Here a DGS tracing of the skull is compared to earlier drawings.

It’s notable
that Pseudocrypturus had long legs. Early ducks, like Presbyornis, and basal raptors, like  Sagittarius, also had long legs. Evidence appears to be building that this was the primitive condition for the clade of living birds.

Figure 2. Pseudocrypturus skull in plate and counter plate plus color tracings and a reconstruction. Note the tiny postorbital. It's on its way out.

Figure 3. Pseudocrypturus skull in plate and counter plate plus color tracings and a reconstruction. Note the tiny postorbital. It’s on its way out.

In the large reptile tree
(LRT, 1059 taxa) Pseudocrypturus nests where Houde 1986 nested it.

Figure 1. Extant birds and their kin. Hummingbirds and their kin and penguins and their kin have been added using the same list of 230 or so characters that have served to nest reptiles, including mammals.

Figure 1. Extant birds and their kin. Hummingbirds and their kin and penguins and their kin have been added using the same list of 230 or so characters that have served to nest reptiles, including mammals.

Good to again confirm
earlier nestings. Not sure how many or which birds to consider next.

References
Houde PW 1986. Ostrich ancestors found in the northern hemisphere suggest new hypothesis of ratite origins. Nature 324:563–565.
Houde PW 1988. Paleognathus birds from the early Tertiary of the northern hemisphere. Publications of the Nuttall Ornithological Club 22. 147 pp.

wiki/Pseudocrypturus

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