Browsing by Author "Surya, Kevin"

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Avian tail ontogeny, pygostyle formation, and interpretation of juvenile Mesozoic specimens
(2018-06) Rashid, Dana J.; Surya, Kevin; Chiappe, Luis M.; Carroll, Nathan; Garrett, Kimball L.; Varghese, Bino; Bailleul, Alida M.; O'Connor, Jingmai K.; Chapman, Susan C.; Horner, John R.
The avian tail played a critical role in the evolutionary transition from long- to short-tailed birds, yet its ontogeny in extant birds has largely been ignored. This deficit has hampered efforts to effectively identify intermediate species during the Mesozoic transition to short tails. Here we show that fusion of distal vertebrae into the pygostyle structure does not occur in extant birds until near skeletal maturity, and mineralization of vertebral processes also occurs long after hatching. Evidence for post-hatching pygostyle formation is also demonstrated in two Cretaceous specimens, a juvenile enantiornithine and a subadult basal ornithuromorph. These findings call for reinterpretations of Zhongornis haoae, a Cretaceous bird hypothesized to be an intermediate in the long- to short-tailed bird transition, and of the recently discovered coelurosaur tail embedded in amber. Zhongornis, as a juvenile, may not yet have formed a pygostyle, and the amber-embedded tail specimen is reinterpreted as possibly avian. Analyses of relative pygostyle lengths in extant and Cretaceous birds suggests the number of vertebrae incorporated into the pygostyle has varied considerably, further complicating the interpretation of potential transitional species. In addition, this analysis of avian tail development reveals the generation and loss of intervertebral discs in the pygostyle, vertebral bodies derived from different kinds of cartilage, and alternative modes of caudal vertebral process morphogenesis in birds. These findings demonstrate that avian tail ontogeny is a crucial parameter specifically for the interpretation of Mesozoic specimens, and generally for insights into vertebrae formation.
Detecting punctuated evolution in SARS-CoV-2 over the first year of the pandemic
(Frontiers Media SA, 2023-02) Surya, Kevin; Gardner, Jacob D.; Organ, Chris L.
The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) evolved slowly over the first year of the Coronavirus Disease 19 (COVID-19) pandemic with differential mutation rates across lineages. Here, we explore how this variation arose. Whether evolutionary change accumulated gradually within lineages or during viral lineage branching is unclear. Using phylogenetic regression models, we show that ~13% of SARS-CoV-2 genomic divergence up to May 2020 is attributable to lineage branching events (punctuated evolution). The net number of branching events along lineages predicts ~5% of the deviation from the strict molecular clock. We did not detect punctuated evolution in SARS-CoV-1, possibly due to the small sample size, and in sarbecovirus broadly, likely due to a different evolutionary process altogether. Punctuation in SARS-CoV-2 is probably neutral because most mutations were not positively selected and because the strength of the punctuational effect remained constant over time, at least until May 2020, and across continents. However, the small punctuational contribution to SARS-CoV-2 diversity is consistent with the founder effect arising from narrow transmission bottlenecks. Therefore, punctuation in SARS-CoV-2 may represent the macroevolutionary consequence (rate variation) of a microevolutionary process (transmission bottleneck).
Distal spinal nerve development and divergence of avian groups
(2020-04) Rashid, Dana J.; Bradley, Roger S.; Bailleul, Alida; Surya, Kevin; Woodward, Holly; Wu, Ping; Wu, Yun-Hsin; Menke, Douglas; Minchey, Sergio; Parrott, Ben; Bock, Samantha; Merzdorf, Christa; Narotzky, Emma; Burke, Nathan; Horner, John R.; Chapman, Susan
The avian transition from long to short, distally fused tails during the Mesozoic ushered in the Pygostylian group, which includes modern birds. The avian tail embodies a bipartite anatomy, with the proximal separate caudal vertebrae region, and the distal pygostyle, formed by vertebral fusion. This study investigates developmental features of the two tail domains in different bird groups, and analyzes them in reference to evolutionary origins. We first defined the early developmental boundary between the two tail halves in the chicken, then followed major developmental structures from early embryo to post-hatching stages. Differences between regions were observed in sclerotome anterior/posterior polarity and peripheral nervous system development, and these were consistent in other neognathous birds. However, in the paleognathous emu, the neognathous pattern was not observed, such that spinal nerve development extends through the pygostyle region. Disparities between the neognaths and paleognaths studied were also reflected in the morphology of their pygostyles. The ancestral long-tailed spinal nerve configuration was hypothesized from brown anole and alligator, which unexpectedly more resembles the neognathous birds. This study shows that tail anatomy is not universal in avians, and suggests several possible scenarios regarding bird evolution, including an independent paleognathous long-tailed ancestor.
Ecological dichotomies arise in microbial communities due to mixing of deep hydrothermal waters and atmospheric gas in a circumneutral hot spring.
(American Society for Microbiology, 2021-09) Fernandes-Martins, Maria C.; Keller, Lisa M.; Munro-Ehrlich, Mason; Zimlich, Kathryn R.; Mettler, Madelyn K.; England, Alexis M.; Clare, Rita; Surya, Kevin; Shock, Everett L.; Colman, Daniel R.; Boyd, Eric S.
Understanding the source and availability of energy capable of supporting life in hydrothermal environments is central to predicting the ecology of microbial life on early Earth when volcanic activity was more widespread. Little is known of the substrates supporting microbial life in circumneutral to alkaline springs, despite their relevance to early Earth habitats.
Pelvic Sexual Dimorphism in Modern Birds (Aves: Neornithes) and Its Evolutionary Relationship with Relative Egg Size
(Montana State Univeristy, 2017-04) Surya, Kevin; Brenes, Isabelle
Pelvic evolution from non-avian to avian dinosaurs (modern birds) is often assessed biomechanically, with functions ranging from weight-carrying, ventilation, and locomotion/flight. Recently, reproduction has been hypothesized to have constrained and shaped pelvic morphology along this lineage. Opening of the pelvis by separating the pubes is thought to have allowed an increase in relative egg size and changes in the egg shape. Since reproductive ability would be advantageous for females, pelvic dimorphism may have evolved in this group. Pelvic dimorphism and its correlation with reproduction in non-avian reptiles and mammals have been extensively studied, but not in modern birds. We are currently investigating pelvic size dimorphism using a multiple regression on representative species from the major group of modern birds (n=30). This will test if there is a significant difference in pelvis dimensions between sexes after accounting for body size. We will also use phylogenetic regression to test for a correlation between dimorphism and relative egg size. Completion of this study will not only result in a better understanding of how the avian pelvis evolved, but also of how sexual selection modifies skeletal anatomy. It is possible that the outcomes of this research will produce a reliable method for determining the sex of extinct dinosaurs, which has been a major hurdle to paleobiological research.