Kansasiella eatoni

Kansasiella eatoni

The two specimens of Ka. eatoni here examined are FMNH UF464 and FMNH UF462, both phosphatic nodules loaned from the Field Museum in Chicago. They were collected from a thin band of yellow-grey shale above the marine Haskell Limestone and below the brackish Robbins Shale of the Douglas Group near Lawrence, Kansas, along with over 400 other nodules ascribed to Kansasiella ( Poplin, 1974) . These nodules were likely formed in a near-shore shallow marine subtropical environment, and have been dated to the Virgilian, Upper Pennsylvanian (305–299 ± 0.8 Mya) ( Miller & Swineford, 1957; Poplin, 1974; Hamel & Poplin, 2008). Neither specimen is complete, though they complement one another near perfectly. The exterior surface of FMNH UF462 is well preserved including the occipital, otic, sphenoid and ventral portion of the ethmoid, but the large crack running through the centre of the nodule obscures the interior and back of the orbit. In contrast, FMNH UF464 has an exquisitely detailed otic and sphenoid region, including fine internal and postorbital features, but is entirely lacking the occipital, ethmoid and ventral parts of the neurocranium. Digital superposition of the two specimens revealed an exact morphological match (after accounting for a 2% global upscaling of FMNH UF162), and the resulting combined reconstruction is shown in all subsequent figures.

IMAGING

Fossil specimens were scanned at the University of Chicago X-ray μCT facility, on a GE Phoenix 240/180 scanner. Parameters used were voltage 130 kV, current 170 μA, timing 500 s and a 0.5 mm Cu filter for P10419a & b, and voltage 130 kV, current 170 μA, timing 500 s and no filter for FMNH UF462 and FMNH UF464. Wet specimens were stained in 5% phosphotungstic acid (PTA) in alcohol for 2 weeks and then scanned with the parameters voltage 75 kV, current 140 uA, timing 1000 s and no filter.

Segmentation and anatomical reconstruction were accomplished using MATERIALISE MIMICS v.19 ( Materialise Mimics, 2016). Imaging of digital models was completed using BLENDER v.2.8 ( Community, 2018). Photography of fossils was accomplished with a Leica DFC490 camera attached to a Zeiss Stemi SV6 microscope and the images processed in IMAGE-PRO PLUS v.6.2 using the enhanced depth of field function to align and process multiple z-stacks of images.

PHYLOGENETIC METHODS