Sinornithosaurus form from those found on birds from the same geological deposits. The body (contour) feathers were generally between 3-4.5 cm long and included two types: the first type are formed of several filaments joined together into "tufts", similar to modern down feathers. The second type, including those on the arms, were composed of rows of filaments ("barbs") joined together along a main shaft ("rachis"), making them similar in structure to modern bird feathers. However, unlike the wing feathers of flying birds, they did not have the secondary branches with tiny little hooks ("barbules") that flight feathers have, which allow the
Calamus Creek (Wisconsin) with drumlins and scattered muck deposits. Soils are predominantly well drained silt over calcareous sandy loam till." The original vegetation cover is primarily white oak, black oak, bur oak, marsh and sedge meadow, wet prairie, and lowland shrubs. Calamus Creek is part of the larger Upper Rock River Basin. The of the streams comprising the Calamus Creek watershed cover , or 19315 acres, with 54.39 acres covered by five unnamed lakes and 3627.39 acres of wetlands. The watershed includes extensive wetlands, some of which are in the process of restoration. Parts of Calamus Creek are designated wadable nursery waters for