Both models are available in coupe and convertible forms
The XK Dynamic R has a top speed of 174mph
Inside, both models get new leather trim
Two new special editions of the Jaguar XK, designed to offer improved luxury or a higher standard of dynamic performance, have been launched.
Dubbed Signature and Dynamic R, the new models are priced from £54,950 and £69,950 respectively. As part of the 2014 model changes Portfolio specification has been axed, with the range taking a price cut of around £10,000.
The new XK Signature model, which is focussed on luxury, features soft-grain leather trim, a suede headlining, polished metal and wood finishes and a reversing camera as standard.
Both coupé and convertible models are offered, with each featuring the XK's naturally aspirated 380bhp 5.0-litre V8.
The Signature can reach 60mph in 5.2sec in coupé guise (increasing to 5.3sec for the convertible) and has a limited top speed of 155mph.
Dynamic R models are based on the XKR, and are endowed with a supercharged 503bhp 5.0-litre V8. It allows the XK Dynamic R to accelerate from 0-60mph in 4.6sec.
Among the upgrades for Dynamic R variants, which are again offered in coupé and drop-top form, is the suspension set-up from the XKR-S. The ride height has also been dropped a further 10mm, and a 'Speed Pack' has been fitted.
The Speed Pack equips the car with aerodynamic improvements, including a front splitter and larger rear spoiler, and a higher 174mph top speed limiter.
Dynamic R models feature Jaguar's Active Differential Control (ADC), which uses a multiplate clutch to vector torque to the wheel with the best traction.
The firm says the ADC technology, coupled with existing ABS and stability control systems, allows the Dynamic R to have greater traction through corners.
Inside, you'll find sports seats that are upholstered in new leather trim; other tweaks for the Dynamic R comprise an active exhaust system.
Both models feature double wishbone front suspension and utilise a new steering knuckle, which Jaguar says increases the steering feedback and weight.
Each sits on 20-inch alloy wheels and uses Jaguar's six-speed automatic transmission, with steering wheel-mounted gearshift paddles.