Creationism in Crisis - Ancestral Geckos from 150 Million Years Before 'Creation Week'

The black banded gecko, Coleonyx fasciatus, is a good approximation of the physical appearance of Helioscopus dickersonae

Francisco Farriols Sarabia
via Wikimedia (CC BY 4.0)

Skeleton of Eichstaettisaurus, an early member of the gecko lineage from the Late Jurassic, Germany

Yale study gives grandmother gecko a place of honor — and a new name | YaleNews

If you want to see the origin of today's species, the best place to find them will be in the fossil record of all the millions of species that lived in that vast expanse of pre-'Creation' time, when some 99.97% of Earth History happened and 99% of all known species lived and went extinct - before creationists believe Earth was created.

For example, and for yet another example of a science paper that casually refutes creationism with no effort to do so on the part of the authors, a team of palaeontologists from Yale have identified a new fossil lizard as the ancestor of modern geckos that lived during the late Jurassic period, 163.5 to 145 million years ago. This pushes the date of the earliest known member of the gecko line in North America back 100 million years.

The team have named the new species, Helioscopus dickersonae and have published their find open access in the journal Proceedings of the Royal Society B. The publication is accompanied by a Yale University press release:

Yale paleontologists have identified a new fossil lizard, found in the western United States, which they say was an ancestor of modern geckos. And they gave it a name that honors the lead researcher’s grandmother and great aunt.

The discovery of the new species, which they named Helioscopus dickersonae, suggests that gecko ancestors appeared in North America much earlier than previously known.

This discovery emerged from a larger investigation of two fossil lizard skulls from Dinosaur National Monument in Utah. These skulls had both been previously described as part of a European genus of skink ancestors, but we wanted to investigate that further with 3D data.

It is one of the earliest known gecko relatives in the fossil record. This means that the gecko line made it to North America nearly 100 million years before the prior known earliest record.

Dalton Meyer, first author
Department of Earth and Planetary Sciences,
Yale University, New Haven, CT, USA.

Specifically, Meyer and his colleagues used computed tomography (CT) scans to develop 3D images of the skulls, which both dated back to the late Jurassic period, 163.5 to 145 million years ago. While one of the skulls was indeed an early skink, the researchers found, the other was not.

CT imagery of the skull of Helioscopus dickersonae

Credit: D. Meyer.

Scientifically, the discovery also offers vital information about specialized physical features of the gecko skull and how they developed. For example, unlike modern geckos, Helioscopus dickersonae was not primarily nocturnal. It had a prominent pineal foramen — a hole in the top of its head that many lizard species use to sense sunlight and judge the length of daylight hours.

Helioscopus dickersonae, Meyer said, was likely similar in appearance to banded geckos or leopard geckos, in that it didn’t have the adhesive toe pads that many modern geckos have. Based on more complete fossil skeletons from similar species found in Europe, he speculated that Helioscopus dickersonae may have been a skilled tree climber even without the toe pads.

Both my grandmother and great aunt were extremely important people in my life, and my great aunt passed away while I was in the early stages of working on this fossil. I was truly honored to have a chance to get to use their family name in this new species, in part as a memorial that will now persist long after I am gone.

Dalton Meyer.

Yet much remains unknown about how this early gecko fared in North America, other than the fact that it went extinct sometime within 90 million years of its arrival on the continent. Nothing like Helioscopus dickersonae appears in the fossil record in the Cretaceous period, which followed the Jurassic.

In naming the new species, Meyer chose “Helioscopus,” which roughly translates into “sun watcher,” and “dickersonae,” which honors his grandmother, Helen Dickerson, his great aunt, Shirley Dickerson, and Mary Cynthia Dickerson (no relation), who was the first curator of herpetology at the American Museum of Natural History in New York City.

Co-authors of the study are Yale graduate students Chase Brownstein and Kelsey Jenkins. The study’s senior author is Jacques Gauthier, professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences and curator-in-charge for reptiles at the Yale Peabody Museum.

Incidentally, note the reason for the generic name of this species, Helioscopus or 'sun watcher' because it has a transitional feature - namely a pineal foramen or hole in the top of its skull to allow sunlight to reach the pineal gland on top of the brain. The pineal gland is associated with circadian rhythms such as sleep-wake cycles. The foramen is a primitive feature not found in later, nocturnal geckos.

What is the evolutionary origin and function of the pineal gland? The pineal gland is a small, pine cone-shaped endocrine gland located in the brain of vertebrates, including humans. Its evolutionary origin can be traced back to early vertebrates, and it is believed to have originated from a light-sensitive organ that detected environmental light changes. In some non-mammalian vertebrates, such as reptiles and birds, the pineal gland is directly sensitive to light and involved in regulating circadian rhythms and seasonal behaviors.

In mammals, including humans, the pineal gland has lost its direct sensitivity to light due to the development of the surrounding brain structures. However, it still plays a crucial role in the regulation of the circadian rhythm, which is the internal biological clock that governs the sleep-wake cycle and other physiological processes over a 24-hour period

The primary function of the pineal gland in mammals is the production of melatonin, a hormone that helps regulate sleep-wake cycles and influences various physiological processes, such as the immune system function and reproductive processes. The secretion of melatonin is influenced by the perception of light through the eyes. When it's dark, the pineal gland is stimulated to produce more melatonin, signaling the body that it is time to sleep. Conversely, exposure to light inhibits melatonin production, signaling that it is time to wake up and be active.

While the evolutionary origin of the pineal gland may have been linked to light sensitivity, its functions in mammals have evolved to be more focused on regulating circadian rhythms and related physiological processes.

The abstract and Introduction to the team's published paper give more technical details and background to the science:

Abstract

Geckos are a speciose and globally distributed clade of Squamata (lizards, including snakes and amphisbaenians) that are characterized by a host of modifications for nocturnal, scansorial and insectivorous ecologies. They are among the oldest divergences in the lizard crown, so understanding the origin of geckoes (Gekkota) is essential to understanding the origin of Squamata, the most species-rich extant tetrapod clade. However, the poor fossil record of gekkotans has obscured the sequence and timing of the assembly of their distinctive morphology. Here, we describe the first North American stem gekkotan based on a three-dimensionally preserved skull from the Morrison Formation of western North America. Despite its Late Jurassic age, the new species already possesses several key characteristics of the gekkotan skull along with retained ancestral features. We show that this new stem gekkotan, and several previously named species of uncertain phylogenetic relationships, comprise a widespread clade of early crown lizards, substantiating faunal homogeneity in Laurasia during the Late Jurassic that extended across disparate ecological, body-size and physiological classes.

1. Introduction Gekkota is a charismatic, speciose, disparate and widely distributed [1] clade of lizards routinely rooting near the base of the lizard tree [2,3]. There are, however, persistent conflicts regarding the position of the root of the squamate crown inferred from molecular versus morphological data [4,5]. Molecular analyses have yet to convincingly resolve relationships among gekkotans, dibamids and unidentatans (all other lizards) that they place at the base of Squamata [2,6]. By contrast, morphological trees [3,7] firmly root between Iguania and the rest of squamates (Scleroglossa), including gekkotans, which are the next crown divergence among scleroglossans. To further complicate matters, molecular analyses never find Iguania as sister to the rest of crown squamates [2]. Despite these complications, the relationships of Gekkota are clearly near the base of the major ‘backbone’ divergences in the lizard crown. Thus, a deeper understanding of gekkotan phylogeny will be vital to resolving the origin of Squamata. Because fossils improve morphological studies [8], the fossil record of Pan-Gekkota, the gecko total clade [9], is expected to play a central role in resolving these conflicts. Unfortunately, that record is poor, particularly in the Mesozoic [10], when most of the squamate backbone clades originated [2,11–13]…

Figure 1. CT Imagery of the skull of Helioscopus dickersonae (DINO 15914). (a,b) In situ skull in dorsal (a) and ventral (b) views. (c–f) Reconstructed skull in left lateral (c), right lateral (d), dorsal (e) and ventral (f) views. All scale bars 5 mm. bc, braincase; ‘cb’, fused postdentary elements (compound bone); d, dentary; f, frontal; j, jugal; m, maxilla; p, parietal; pa, palatine; pf, prefrontal; pof, postorbitofrontal; pt, pterygoid; sq, squamosal.

Figure 4. Evolution of pan-gekkotan anatomy and biogeography. Tree of Pan-Gekkota (from our weighted analysis K = 12 restricted to a molecular topology). Branch squares represent inferred continents of origin, with terminal branches based on recorded observations and internal branches being the results of our parsimony ancestral states reconstruction. Red, Europe; blue, North America; orange, Asia; green, Africa; purple, South America; yellow, Australian plate. New taxa in bold. Circles above branches represent key synapomorphies of Gekkota and Pan-Gekkota identified by [3]. Open circles represent the absence of features, closed circles represent the presence of features, and partially filled circles represent partially acquired features. 1, fusion of the frontals; 2, fusion of the frontal subolfactory processes into a tubular structure; 3, absence of a postorbital; 4, paired parietals; 5, posterior midline projection of the parietal; 6, absence of a pineal foramen; 7, prefrontal medial margin extending beneath frontal subolfactory process; 8, absence of a jugal postorbital bar; 9, edentulous palate (as gauged by the condition of the pterygoid); 10, dentary fused over Meckel's canal; 11, 31 or more maxillary and dentary teeth.

Figure 2. Close-up photographs of Limnoscansor digitatellus (CM 4026). (a) Full body of specimen (dorsal view). (b) Close up of skull (dorsal view).

Figure 5. Historical biogeography of Pan-Gekkota. (a) The distribution of sister taxa found at European and western North American sites. The red dot indicates the hypothesized European origin of Pan-Gekkota and the blue dot represents the previously unknown North American radiation. (b) The phylogeographic hypothesis for pygopodoids generated in this study. The green dot represents the estimated Asian origin of Gekkota and the yellow dot represents the estimated Australian origin of Pygopodoidea. White lines represent the two possible scenarios of pan-pygopodoid dispersal out of Asia supported by this study. Paleogeographic reconstructions constructed with GPlates.

Meyer, Dalton; Brownstein, Chase D.; Jenkins, Kelsey M.; Gauthier, Jacques A.
A Morrison stem gekkotan reveals gecko evolution and Jurassic biogeography
Proceedings of the Royal Society B: Biological Sciences 290 2011 20232284. DOI: 10.1098/rspb.2023.2284

Copyright: © 2023 The authors.
Published by the Royal Society. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

Rather than admit they are wrong, creationists will undoubtedly resort to one of their ludicrously implausible excuses for dismissing evidence such as this.

For example, the dating is wrong because radioactive decay rates have changed to make 150 million years look like 10,000, even though that would have made life impossible when it was allegedly created, or the millions of working biomedical scientists who, almost without exception, accept evolution as the fundamental, unifying principle of biology, their technical and admin staff in the universities and research institutions, and the publishers of scientific journals, are all part of a vast tightly controlled conspiracy, so tightly controlled that no-one ever broke ranks, not even in retirement.

But, despite creationists infantile denialism, abuse of scientists, misrepresentation of the facts and downright lies, the fact remains that there were ancestral geckos living in what is now North America, 150 million years before they believe Earth was magically created out of nothing.

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