Amber from the Pipestone Creek bonebed, Campanian of Canada (1 Viewer)

Pierre Cockxa, Ryan McKellara, Ralf Tappert, Matthew Vavrek, Karlis Muehlenbachs, 2020

Bonebed amber as a new source of paleontological data: The case of the Pipestone Creek deposit (Upper Cretaceous), Alberta, Canada

Gondwana Research(2020), https://doi.org/10.1016/j.gr.2019.12.005

Highlights:

Amber chemistry suggests cupressaceous trees in Late Cretaceous high latitude.

Stable isotope analyses suggest habitat distant from the Western Interior Seaway.

Relatively diverse arthropod, botanical, and vertebrate inclusions are present.

Abstract: https://www.sciencedirect.com/science/article/abs/pii/S1342937X20300198?via=ihub

Amber deposits and dinosaur bonebeds provide some of the most detailed sources of information on terrestrial ecosystems, but these sources have rarely been studied in tandem. The Pipestone Creek bonebed from the Campanian Wapiti Formation of Alberta, Canada, provides an opportunity to explore both data sources in the same deposit for the first time. The site has yielded an exceptional fauna dominated by abundant remains of the centrosaurine ceratopsian Pachyrhinosaurus. The initial campaigns of excavation in the 1980s led to the collateral discovery of amber, and the site became the first published source of insect-bearing amber in a dinosaur bonebed. Here we describe amber inclusions in detail and analyze the composition and geochemistry of the amber (FTIR spectroscopy and stable isotope studies) in order to draw paleoecological and paleoenvironmental inferences. We describe a feather fragment from an aquatic bird, as well as new species of Psocodea and Hymenoptera (Mymarommatidae) with ecological constraints. Indeterminate aphid and spider inclusions were also found, but preservation was not sufficient for formal description. FTIR spectroscopy suggests a botanical source among the Cupressaceae, while stable isotope data indicate that the resin-producing forest did not receive precipitation directly from the Western Interior Seaway. These initial results show that amber is a valuable source of additional information about the habitat surrounding the vertebrates found in bonebed deposits. Given the abundance and range of inclusions encountered so far, Pipestone Creek amber also appears to be a promising new source for a relatively diverse Campanian amber assemblage.

Enjoy,

Fred

Systematic Paleontology

Suborder Theropoda Marsh 1881

Description. TMP 87.55.336 is a small amber fragment (2.7 mm x 1.3 mm) preserving a dense clump of flexible filaments with a mean diameter of approximately 6 μm at most. The filaments lack cell walls (Fig. 2D) and exhibit strong nodal prongs, negating a botanical or fungal origin. The general morphology, with nodes and prongs (Fig. 2C), matches with fragments of feathers previously described in Canadian amber from the Grassy Lake site (McKellar et al., 2011), and is consistent with plumulaceous feather barbules. Barbules display normal nodes (sensu Dove, 2000), and lengths of prongs and internodes vary between individual barbules. Pigmentation is diffuse and irregular, with some barbules displaying a concentration in their nodes and prongs. Pigmented areas appear dark while other areas are transparent suggesting that the feather had a pale or white color in life.

Discussion. Comparison between TMP 87.55.336 and modern feathers may suggest taxonomic affinities, but it is more likely that the unusual barbule morphology is related to ecology. The fossil barbules are similar to those observed in some aquatic birds, such as the Galapagos penguin (Spheniscus mendiculus Sundevall, 1871), or the sooty shearwater (Ardenna grisea Gmelin, 1789), which both have long nodal prongs (Chandler, 1916). Based upon the preserved feather morphology and regional fossil record for Late Cretaceous birds, it seems likely that the feather fragments came from an aquatic or shore bird. Members of Hesperornithes and Ichthyornithes, two groups containing semiaquatic representatives, extended across much of North America in the Late Cretaceous (Longrich et al., 2011; Wilson et al., 2011), and seem to be the most likely source animals for the amberentombed feather fragments.

Fred

Fig. 1. Feather fragment TMP 87.55.336 in Pipestone Creek amber. A) Sample overview, dark field. B)
Sample overview, transmitted light. C) Filament with nodes, prongs and pigmentation visible. D)
Filament. E) Curved filaments. Scale bars = A–B: 1 mm; C: 0.05 mm; D–E: 0.1 mm.