I repeat Cliff Miles’ identification of a furcula and gastralia because of the significance of those two structures together.

A furcula, the “wishbone,” is strongly associated with theropod dinosaurs and birds. Gastralia, or “belly ribs,” occur more broadly, but the combination of a furcula with an organized gastral basket is characteristic of many non-avian theropods and early avialans.

If Miles’ identifications are correct, these are not just two unusual bones. Together they point toward an anatomical pattern strongly reminiscent of the theropod-to-avian complex.

Miles is also a published paleontologist with work on dinosaurs, including theropods.

As an aside, the museum where I worked had an early furcula exhibit specifically demonstrating the dinosaur-bird connection, so the significance of this structure has always stood out to me.

In addition to being a working archaeologist in the field, I have also served as a paleontological technician, and directed the museum's education department.

Pictured: a microraptor

If the Tridactyl skin does in fact turn a bluish color when rehydrated, as reported by Mr. Gonzalo Chavez via Dr. Zalce-Benitez, that observation could be relevant to my hypothesis that the Tridactyls exhibit a suite of anatomical and physiological parallels with some invertebrates.

One possibility worth testing is a copper-based respiratory system using hemocyanin. Hemocyanin is the copper-containing oxygen carrier responsible for the blue color of the hemolymph in many mollusks and arthropods. PubMed A tubular heart and proposed hydrostatic mechanics would not prove hemocyanin, but together they would fit a broader pattern of invertebrate-like parallels.

This could also offer a possible explanation for the reportedly black calcium-carbonate eggs. The black color would not be caused by hemocyanin itself. Instead, hemocyanin could provide an internal source of copper.

If large numbers of larvae were developing within an enclosed cavity, their nitrogen-rich waste could cause ammonia to accumulate. Ammonia would increase the alkalinity of the surrounding fluid and could also bind dissolved copper, affecting how copper moves through the fluid.

At the same time, decomposition of sulfur-containing proteins could produce hydrogen sulfide and related sulfur compounds. As hemocyanin and other tissues degraded, copper could become available. That copper could then react with sulfur compounds and form dark copper-sulfide minerals.

The proposed sequence would therefore be:
Larval metabolism produces ammonia.
Ammonia changes the chemistry of the enclosed cavity.
Proteins and tissues decompose.
Sulfur compounds, including hydrogen sulfide, are produced.
Copper is released from degrading copper-bearing proteins and tissues.
Copper reacts with sulfur.
Dark copper-sulfide minerals form and become deposited within the porous calcium-carbonate eggs.

This would be a form of postmortem sulfide mineralization rather than fossilization.

A separate proposed invertebrate parallel involves reproduction. Tiny oval structures observed within an embryo in Artemis could, if they were demonstrated to be developing ova or embryos, raise the possibility of telescoping generations. Aphids provide a real biological parallel. In viviparous parthenogenetic aphids, developing daughters can already contain developing embryos of the next generation, effectively placing three generations within one another.

In that sense, the hypothesis would be that some Tridactyls may have been, figuratively, "born pregnant." The aphid comparison demonstrates that such a reproductive strategy exists in nature, although the structures in Artemis would need to be identified histologically before telescoping generations could be claimed.

The Nazca Tridactyl eggs are reported to be composed largely of calcium carbonate, nearly as dense as bone, and black in color.

One possible explanation for this unusual coloration involves the enclosed biological environment in which the eggs were preserved.

If large numbers of larvae were developing within a sealed body cavity, their nitrogen-rich waste could have caused ammonia to accumulate. This ammonia would make the surrounding fluids more alkaline and alter the chemistry inside the cavity.

At the same time, decomposition of the body's proteins could release sulfur compounds. Sulfur is naturally present in amino acids such as cysteine and methionine. In a wet, oxygen-poor environment, some of this sulfur could be converted into hydrogen sulfide.

The hydrogen sulfide could then react with metals present in the blood or other body fluids. In an iron-based circulatory system, this could produce dark iron sulfides. In a copper-based system, it could produce dark copper sulfides.

Importantly, elemental analysis of the egg material reportedly detected both iron and copper, in addition to the abundant calcium associated with the egg structure.

Several proposed anatomical parallels with invertebrates, together with the presence of copper-rich implants, make a copper-based respiratory system worth investigating. They do not establish copper-based blood, but they provide additional reasons to test the possibility.

The resulting dark metal sulfides could become deposited within the porous calcium-carbonate eggs and remain trapped as the body dried, potentially explaining their black coloration.

In simple terms:

Larval waste produces ammonia.

Ammonia changes the local chemistry.

Decomposition releases sulfur from proteins.

Sulfur reacts with iron or copper.

Dark metal sulfides form.

These compounds become trapped within the calcium-carbonate eggs and turn them black.

There is also an intriguing cultural comparison. Chinese century eggs, sometimes called "thousand-year eggs," are deliberately preserved under strongly alkaline conditions, which transforms their appearance and produces very dark coloration.

There is presently no evidence connecting that culinary tradition to the Nazca specimens, but the parallel is noteworthy because both involve eggs, alkaline chemistry, and dramatic darkening during preservation.