A new Jurassic theropod from China documents a transitional step in the macrostructure of feathers

“…Another paravian, Serikornis , is preserved with dramatically long, dense contour plumage (Lefèvre et al . ), consistent with the ‘shaggy’ appearance of paravian plumage suggested here. We hypothesize that the ‘shaggy’ plumage of Anchiornis affected physiology by altering heat retention (relative to the combination of modern down and contour feathers), decreasing water repellence, and decreasing aerodynamic efficiency by increasing drag in comparison to modern feathers, which are known to function effectively in such roles (Lucas & Stettenheim ).…”

“…Although Lefèvre et al . () suggested that barbules were entirely lacking in Serikornis , this is unlikely and represents an extreme interpretation, as discussed above where the presence of iridescence in paravians is consistent with the likely presence of barbules (Maia et al . ; Li et al .…”

“…The clades Oviraptorosauria, Troodontidae, and Avialae are recovered as monophyletic while Dromaeosauridae sensu lato is not recovered. The results from our test of the TWiG matrix agree with those of some previous phylogenetic analyses (Xu et al, 2011;Agnolin and Novas, 2013;Lefèvre et al, 2017;Cau, 2018) in suggesting that the traditional concepts of Deinonychosauria and Dromaeosauridae rest on weak evidence and lack strong anatomical support. Because of the poor resolution obtained from analysis of the TWiG matrix, we opt not to follow these phylogenetic results, and instead present below our own interpretations of the possible phylogenetic affinities of each of these paravian subclades based on a review of the available morphological evidence.…”

“…analyses (e.g., Novas and Pol, 2005;Senter, 2007;Hu et al, 2009Hu et al, , 2018Novas et al, 2009;Xu et al, 2011;Turner et al, 2012;Godefroit et al, 2013a,b;Cau et al, 2017;Foth and Rauhut, 2017;Gianechini et al, 2017Gianechini et al, , 2018Lefèvre et al, 2017). In contrast, Novas (2011, 2013; see also Novas et al, 2018) regarded unenlagiids as stem Avialae, in agreement with the original description of Unenlagia (Novas and Puerta, 1997).…”

“…Serrations are small (5.5 per mm distally) as in Sinusonasus , Liaoningvenator and some sinovenatorines, and not apically hooked. Similar to the condition described for Serikornis , the maxillary teeth are anisodont with crown height of the largest exposed teeth twice the size of others (Lefèvre et al, 2017: Fig. 2).…”

“…Another paravian, Serikornis , is preserved with dramatically long, dense contour plumage (Lefèvre et al . ), consistent with the ‘shaggy’ appearance of paravian plumage suggested here. We hypothesize that the ‘shaggy’ plumage of Anchiornis affected physiology by altering heat retention (relative to the combination of modern down and contour feathers), decreasing water repellence, and decreasing aerodynamic efficiency by increasing drag in comparison to modern feathers, which are known to function effectively in such roles (Lucas & Stettenheim ).…”

“…Although Lefèvre et al . () suggested that barbules were entirely lacking in Serikornis , this is unlikely and represents an extreme interpretation, as discussed above where the presence of iridescence in paravians is consistent with the likely presence of barbules (Maia et al . ; Li et al .…”

“…The clades Oviraptorosauria, Troodontidae, and Avialae are recovered as monophyletic while Dromaeosauridae sensu lato is not recovered. The results from our test of the TWiG matrix agree with those of some previous phylogenetic analyses (Xu et al, 2011;Agnolin and Novas, 2013;Lefèvre et al, 2017;Cau, 2018) in suggesting that the traditional concepts of Deinonychosauria and Dromaeosauridae rest on weak evidence and lack strong anatomical support. Because of the poor resolution obtained from analysis of the TWiG matrix, we opt not to follow these phylogenetic results, and instead present below our own interpretations of the possible phylogenetic affinities of each of these paravian subclades based on a review of the available morphological evidence.…”

“…analyses (e.g., Novas and Pol, 2005;Senter, 2007;Hu et al, 2009Hu et al, , 2018Novas et al, 2009;Xu et al, 2011;Turner et al, 2012;Godefroit et al, 2013a,b;Cau et al, 2017;Foth and Rauhut, 2017;Gianechini et al, 2017Gianechini et al, , 2018Lefèvre et al, 2017). In contrast, Novas (2011, 2013; see also Novas et al, 2018) regarded unenlagiids as stem Avialae, in agreement with the original description of Unenlagia (Novas and Puerta, 1997).…”

“…Serrations are small (5.5 per mm distally) as in Sinusonasus , Liaoningvenator and some sinovenatorines, and not apically hooked. Similar to the condition described for Serikornis , the maxillary teeth are anisodont with crown height of the largest exposed teeth twice the size of others (Lefèvre et al, 2017: Fig. 2).…”

“…Another paravian, Serikornis , is preserved with dramatically long, dense contour plumage (Lefèvre et al . ), consistent with the ‘shaggy’ appearance of paravian plumage suggested here. We hypothesize that the ‘shaggy’ plumage of Anchiornis affected physiology by altering heat retention (relative to the combination of modern down and contour feathers), decreasing water repellence, and decreasing aerodynamic efficiency by increasing drag in comparison to modern feathers, which are known to function effectively in such roles (Lucas & Stettenheim ).…”

“…Although Lefèvre et al . () suggested that barbules were entirely lacking in Serikornis , this is unlikely and represents an extreme interpretation, as discussed above where the presence of iridescence in paravians is consistent with the likely presence of barbules (Maia et al . ; Li et al .…”

“…The clades Oviraptorosauria, Troodontidae, and Avialae are recovered as monophyletic while Dromaeosauridae sensu lato is not recovered. The results from our test of the TWiG matrix agree with those of some previous phylogenetic analyses (Xu et al, 2011;Agnolin and Novas, 2013;Lefèvre et al, 2017;Cau, 2018) in suggesting that the traditional concepts of Deinonychosauria and Dromaeosauridae rest on weak evidence and lack strong anatomical support. Because of the poor resolution obtained from analysis of the TWiG matrix, we opt not to follow these phylogenetic results, and instead present below our own interpretations of the possible phylogenetic affinities of each of these paravian subclades based on a review of the available morphological evidence.…”

“…analyses (e.g., Novas and Pol, 2005;Senter, 2007;Hu et al, 2009Hu et al, , 2018Novas et al, 2009;Xu et al, 2011;Turner et al, 2012;Godefroit et al, 2013a,b;Cau et al, 2017;Foth and Rauhut, 2017;Gianechini et al, 2017Gianechini et al, , 2018Lefèvre et al, 2017). In contrast, Novas (2011, 2013; see also Novas et al, 2018) regarded unenlagiids as stem Avialae, in agreement with the original description of Unenlagia (Novas and Puerta, 1997).…”

“…Serrations are small (5.5 per mm distally) as in Sinusonasus , Liaoningvenator and some sinovenatorines, and not apically hooked. Similar to the condition described for Serikornis , the maxillary teeth are anisodont with crown height of the largest exposed teeth twice the size of others (Lefèvre et al, 2017: Fig. 2).…”