Fourier transform infrared spectroscopy of the saddle

As the key component of the striking system, the saddle comprised two distinct layers including outer layer and inner layer. The outer layer contained blocky microtubules and exhibited compact appearance.

The inner layer presented a typical periodic lamellar structure. Due to the change of the thickness of the mineralized outer layer, the organic multilamellar structure became the foundation and enhanced the connection strength (4.55 MPa) at the connect regions between the saddle and merus exoskeleton and membrane, respectively. In the process of fracture, the lamellar structure dispersed the stress effectively by the change of the crack deflection direction and the microfibrils ordered arrangement.