Darwin’s finches: Mesozoic style

Originally ‘Darwin’s finches’ =
small birds from the Galápagos Islands west of Ecuador, in the Pacific Ocean.

According to Wikipedia:
The term “Darwin’s finches” was first applied by Percy Lowe in 1936, and popularised in 1947 by David Lack in his book Darwin’s Finches. The most important differences between species are in the size and shape of their beaks, which are highly adapted to different food sources.”

For today’s post, metaphorically speaking, ‘Darwin’s finches’ =
“several variations on a last common ancestor restricted to a small geographic area.”

Similar Mesozoic variations
on a last common ancestor restricted to a small geographic area are also documented in the large reptile tree (LRT) and the large pterosaur tree (LPT). Here (Figs. 1–8), other than Late Cretaceous Pteranodon (Fig. 1), and Middle Jurassic Darwinopterus (Fig. 8), the others (Figs. 2–7), are all known from the Late Jurassic Solnhofen Formation, a lagerstätte representing an archipelago or series of islands, much like today’s Galápagos Islands.

Here
(Figs. 1–8) pictures of closely related taxa tell the story of their own evolution much better than any long-winded explanation. No two are alike. Arrows indicate phylogenetic order.

If you want to know more,
click on each of the images below. When taken to the large image pages at ReptileEvolution.com a small link at the top of each page will take you to one of the species pictured therein. Other links to related taxa are posted on each species’ page.

Pteranodon

Figure 2. The DMNH specimen is in color, nesting between the short crest KS specimen and the long crest AMNH specimen.

Figure 1. The DMNH specimen is in color, nesting between the short crest KS specimen and the long crest AMNH specimen. If you see a female in this diagram, let me know. No two are alike.

Rhamphorhynchus

Figure 2. Rhamphorhynchus specimens to scale. The Lauer Collection specimen would precede the Limhoff specimen on the second row.

Figure 2. Rhamphorhynchus specimens to scale. The Lauer Collection specimen would precede the Limhoff specimen on the second row. No two are alike, but the Vienna specimen is a juvenile of the larger n81 specimen to its right.

Dorygnathus

Figure 8. Click to enlarge. The descendants of Sordes in the Dorygnathus clade and their two clades of pterodactyloid-grade descendants.

Figure 3. Click to enlarge. The descendants of Sordes in the Dorygnathus clade and their two clades of pterodactyloid-grade descendants. No two are alike.

Germanodactylus

Germanodactylus and kin

Figure 4. Click to enlarge. Germanodactylus and kin. No two are alike.

Pterodactylus

The Pterodactylus lineage and mislabeled specimens formerly attributed to this "wastebasket" genus

Figure 5. Click to enlarge. The Pterodactylus lineage (in white) and mislabeled specimens formerly attributed to this “wastebasket” genus (in color boxes). No two are alike.

Scaphognathus

Figure 1. Scaphognathians to scale. Click to enlarge.

Figure 6. Click to enlarge. Only the left three taxa have been identified as Scaphognathus species. Other tiny unnamed specimens are transitional taxa to Pterodactylus or Germanodactylus leading to larger, later taxa. No two are alike.

Archaeopteryx (some of these Solnhofen birds have been renamed)

Figure 3. Several Solnhofen birds, including Archaeopteryx, compared to Ostromia to scale.

Figure 7. Several Solnhofen birds, including Archaeopteryx, compared to Ostromia to scale. No two are alike.

Darwinopterus

Figure 7. Darwinopterus specimens and a few outgroup taxa.

Figure 8. Darwinopterus specimens and a few outgroup taxa. None of these are basal to any pterodactyloid-grade clades. No two are alike. The female (upper right) is associates with an egg.

Unfortunately,
PhDs and other paleo workers who traditionally refuse to trace and reconstruct ‘to scale’ skeletons of taxa under study never get to discover results like these that are only revealed from producing ‘to scale’ graphics like these (Figs. 1–8). Subtleties come through here, en masse, that are lost when looking at individual skeletons in situ one at a time, especially through a microscope, where you don’t get to see ‘the big picture’. Some workers consider such graphics pseudoscience and crankery.

As a result, no other workers
understand or accept the four origins of the pterodactyloid grade arising from phylogenetic miniaturized transitional taxa (Figs. 3, 6) because they omit pertinent tiny and congeneric taxa. Likewise, workers do not yet understand nor accept the radiation of several bird clades having their genesis in Solnhofen basalmost birds. Workers don’t see ‘the big picture’ because of these taxon exclusions.

Rather, too many workers
try to compile a list of specific traits that differentiate one taxon from another. Here we call that, “Pulling a Larry Martin” because it only sometimes leads to greater understanding. The problem is unrelated taxa too often share those same traits by convergence. Here, reconstructions and a confident nesting in the LRT automatically encompass and include ALL the subtle irregularities between taxa that ‘trait seekers’ traditionally overlook.

References

wiki/Darwin’s_finches

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